Biomedical subjects

Luigi Palmieri

Publications and source records attributed to Luigi Palmieri.

At least 19 recordsLinked to original sources

PubMed2026

Evolutionary history and recombination in the mitochondrial carrier SLC25 superfamily analyzed by similarities in the exon and transmembrane α-helix sequences.

Mitochondrial carriers (MCs), which constitute a superfamily also called the solute carrier family 25 (SLC25), are characterized by conserved signature motif sequences and a six-transmembrane α-helical transporter domain. They transport a wide variety of substrates ranging from protons, inorganic ions, citric acid cycle intermediates, and amino acids to nucleotides and cofactors. The superfamily members can be divided into subfamilies, each with a distinct substrate specificity. In an attempt to understand how different subfamilies have evolved, we analyzed the protein sequences of the exons (with conserved boundaries) and the six transmembrane α-helices of MCs from highly diverged organisms. The results show that some MC subfamilies have all exons and transmembrane α-helices most similar to a closely related subfamily, which is consistent with a scenario of gene duplication and mutational divergence from a last common ancestor. However, several MC subfamilies appear to be mosaics of exons and transmembrane α-helices most similar to different and distant subfamilies, which in some cases could be explained by recombination between the superfamily genes during evolution. It seems that this latter mechanism could have played a role in the formation of new subfamilies with different substrate specificities by the combination of MC transporter domain segments that had been optimized previously for binding specific portions of the substrates. This study presents novel evolutionary relationships between MC subfamilies and may provide clues for how protein superfamilies have expanded and how to investigate their evolution.

Evolution, Molecular↗

PubMed2006

Molecular identification of an Arabidopsis S-adenosylmethionine transporter. Analysis of organ distribution, bacterial expression, reconstitution into liposomes, and functional characterization.

Despite much study of the role of S-adenosylmethionine (SAM) in the methylation of DNA, RNA, and proteins, and as a cofactor for a wide range of biosynthetic processes, little is known concerning the intracellular transport of this essential metabolite. Screening of the Arabidopsis (Arabidopsis thaliana) genome yielded two potential homologs of yeast (Saccharomyces cerevisiae) and human SAM transporters, designated as SAMC1 and SAMC2, both of which belong to the mitochondrial carrier protein family. The SAMC1 gene is broadly expressed at the organ level, although only in specialized tissues of roots with high rates of cell division, and appears to be up-regulated in response to wounding stress, whereas the SAMC2 gene is very poorly expressed in all organs/tissues analyzed. Direct transport assays with the recombinant and reconstituted SAMC1 were utilized to demonstrate that this protein displays a very narrow substrate specificity confined to SAM and its closest analogs. Further experiments revealed that SAMC1 was able to function in uniport and exchange reactions and characterized the transporter as highly active, but sensitive to physiologically relevant concentrations of S-adenosylhomocysteine, S-adenosylcysteine, and adenosylornithine. Green fluorescent protein-based cell biological analysis demonstrated targeting of SAMC1 to mitochondria. Previous proteomic analyses identified this protein also in the chloroplast inner envelope. In keeping with these results, bioinformatics predicted dual localization for SAMC1. These findings suggest that the provision of cytosolically synthesized SAM to mitochondria and possibly also to plastids is mediated by SAMC1 according to the relative demands for this metabolite in the organelles.

Amino Acid Sequence↗

PubMed2006

Identification of mitochondrial carriers in Saccharomyces cerevisiae by transport assay of reconstituted recombinant proteins.

The inner membranes of mitochondria contain a family of carrier proteins that are responsible for the transport in and out of the mitochondrial matrix of substrates, products, co-factors and biosynthetic precursors that are essential for the function and activities of the organelle. This family of proteins is characterized by containing three tandem homologous sequence repeats of approximately 100 amino acids, each folded into two transmembrane alpha-helices linked by an extensive polar loop. Each repeat contains a characteristic conserved sequence. These features have been used to determine the extent of the family in genome sequences. The genome of Saccharomyces cerevisiae contains 34 members of the family. The identity of five of them was known before the determination of the genome sequence, but the functions of the remaining family members were not. This review describes how the functions of 15 of these previously unknown transport proteins have been determined by a strategy that consists of expressing the genes in Escherichia coli or Saccharomyces cerevisiae, reconstituting the gene products into liposomes and establishing their functions by transport assay. Genetic and biochemical evidence as well as phylogenetic considerations have guided the choice of substrates that were tested in the transport assays. The physiological roles of these carriers have been verified by genetic experiments. Various pieces of evidence point to the functions of six additional members of the family, but these proposals await confirmation by transport assay. The sequences of many of the newly identified yeast carriers have been used to characterize orthologs in other species, and in man five diseases are presently known to be caused by defects in specific mitochondrial carrier genes. The roles of eight yeast mitochondrial carriers remain to be established.

Biological Transport↗

PubMed2006

Arabidopsis mitochondria have two basic amino acid transporters with partially overlapping specificities and differential expression in seedling development.

To shed light on the metabolic role of two mitochondrial transporters for basic amino acids in Arabidopsis, we compared their functional properties in liposomes and expression during germination. Recombinant and purified BAC2, as previously reported for BAC1, transported various basic L-amino acids upon reconstitution in phospholipid vesicles. Both displayed highest affinity for arginine with similar Km and Vmax. However, BAC2 transported citrulline for which BAC1 had little or no affinity. Furthermore, BAC2 was less stereospecific than BAC1, transporting D-arginine and D-lysine at significant rates, and displayed a striking alkaline pH optimum (pH 8.0) whereas BAC1 activity was unaltered from pH 7.0 to 9.0. By semi-quantitative RT-PCR BAC1 transcript levels were found to be higher than those of BAC2 in germinated seeds. However, BAC2 expression transiently increased 2 days after germination. Disruption of the Arabidopsis arginase structural genes (ARGAH1 or ARGAH2) accentuated the increases of transcript levels of BAC1 at germination and of BAC2 2 days after germination and from 6 days on. Early expression of BAC1 and BAC2 is consistent with the delivery of arginine, released from seed reserves, to mitochondrial arginase and the export of ornithine. Increase of BAC2 transcript levels later in seedling development is consistent with roles in NO, polyamine or proline metabolism--processes involving arginine, citrulline and/or ornithine.

Amino Acid Transport Systems, Basic↗

PubMed2006

Favorable cardiovascular risk profile (low risk) and 10-year stroke incidence in women and men: findings from 12 Italian population samples.

Recently, the focus of research on cardiovascular risk factors has broadened because of new data demonstrating benefits of low risk (i.e., favorable) levels of all major modifiable risk factors. Most data on low risk relate to coronary heart disease, not stroke. This population-based, 12-sample, Italian study (Progetto CUORE, 1983-2002), with 10-year follow-up, assessed the relation of low risk to stroke and implications for prevention. At baseline, women and men were 35-69 years of age. Only 3% were low risk; 80% were high risk. Overall, stroke incidence rates were 20.7 for men and 9.6 for women per 10,000 person-years. No strokes occurred in low risk participants, and stroke incidence was low with borderline elevation of only one risk factor. Four modifiable risk factors--elevated blood pressure, smoking, diabetes, and high total cholesterol/high density lipoprotein cholesterol ratio--related independently to stroke risk. For those at low risk or who had only one unfavorable (but not high) risk factor, the stroke rate was 76% lower than for high risk participants; for all persons not at high risk, the stroke rate was 57% lower than for those at high risk. Results show that favorable risk factor levels assure minimal stroke risk. Population-wide prevention is needed, especially improved lifestyles, to increase the prevalence of low risk.

Adult↗

PubMed2006

Favorable cardiovascular risk profile and 10-year coronary heart disease incidence in women and men: results from the Progetto CUORE.

BACKGROUND: Cardiovascular risk factor research has recently broadened its focus based on new data indicating the benefits of low risk, i.e. favorable levels of all major risk factors. The aims of this study were to assess further the relation of low risk to coronary heart disease risk, and implications for prevention. DESIGN: We conducted a prospective population-based Italian study, of 7438 men and 13 009 women aged 35-69 years, with a mean follow-up of 10.4 years and validated first coronary events. METHODS: Baseline coronary heart disease risk was classified into three categories: low risk; unfavorable but not high risk; and high risk. To analyze the relation of these risk profiles to coronary heart disease incidence, age-adjusted, sex-averaged coronary heart disease incidence was calculated for persons free of coronary heart disease and stroke, stratified as baseline low risk, unfavorable but not high risk or high risk. To assess the independent relationship of individual risk factors to coronary heart disease incidence, multivariate proportional hazards models were computed for combinations of risk factors. RESULTS: Only 2.7% of participants met low risk criteria; 81.4% were high risk. Age-adjusted coronary heart disease incidence for the whole cohort was 37.1 out of 10000 person-years (men 59.0; women 15.3). No coronary heart disease events occurred in low-risk men, only two in low-risk women. For women and men who were not high risk, the age-sex standardized coronary heart disease rate was 62% lower than for high-risk participants. Blood pressure, need for antihypertensive medication, smoking, hyperglycemia, diabetes, total and high-density lipoprotein cholesterol were independently related to coronary heart disease risk. CONCLUSIONS: Favorable levels of all modifiable readily measured risk factors - rare among Italian adults - assure minimal coronary heart disease risk. Population-wide prevention is needed, especially improved lifestyles, to increase the proportion of the population at low risk.

Adult↗

PubMed2006

[Assessment of the absolute global cardiovascular risk: comparison between the risk chart and the individual score of the CUORE Project].

BACKGROUND: To evaluate 10-year cardiovascular risk, the risk chart and the individual risk score from the CUORE Project were recently introduced in Italy. These tools differ as for age range and some risk factors. Therefore, the aim of this study is to evaluate the difference between the global absolute risk assessed by the risk chart and the individual risk score using the data collected through the Osservatorio Epidemiologico Cardiovascolare (OEC). METHODS: From the Osservatorio Epidemiologico Cardiovascolare sample, 6508 people aged 40-69 years without clinical manifestations of atherosclerosis were selected. Cardiovascular risk was assessed using risk chart and individual risk score and the 10-year risk was categorized in six classes (< 5%, 5-9%, 10-14%, 15-19%, 20-29%, > or = 30%). As coefficient of agreement between risk chart and individual risk score, Cohen kappa statistic was computed using the Cicchetti-Allison weights (k(w)). RESULTS: From contingency tables of the two methods distribution, k(w) was 0.71 (p < 0.0001 and 95% confidence interval 0.70-0.72). Using the 20% risk threshold reported in Nota 13 of Agenzia Italiana del Farmaco and excluding persons who were treated for hyperlipemia refunded regardless of their chart or individual score estimation of cardiovascular risk, the differences between the two tools classification resulted in the 2.6% of the sample (1.4% were assessed as at non-high risk [< 20%] using the risk chart and at high risk using the individual risk score, and the opposite for 1.2%). CONCLUSIONS: Classification difference between risk charts and the individual risk score is quite small. Updating of predictive functions of two tools could improve their concordance also for individual evaluation, including older people and better reflecting current Italian lifestyle.

Adult↗

PubMed2006

[Occupational and leisure time physical activity: trend in the Italian population].

BACKGROUND: Over the last decades a change in physical activity habits of the Italian population has been observed. The aim of this study was to compare occupational and leisure-time physical activity, to assess the relationship between physical activity and cardiovascular risk factors and the variation in cardiovascular risk profile measured 20 years apart in the Italian population. METHODS: In two populations aged 35-69 years (MATISS 1984-1987: 2041 men, 2424 women; OEC 1998-2002: 4214 men, 4206 women) gender-specific levels of occupational (occupational physical activity [OPA]-light, OPA-moderate, OPA-heavy) and leisure-time (leisure-time physical activity [LTPA]-low, LTPA-moderate, LTPA-high) physical activity were compared. Relationship between physical activity and cardiovascular risk factors was evaluated in the two samples using logistic regression models adjusted for age, heart rate, educational level and other possible confounding variables in men and women separately. The 10-year cardiovascular risk was assessed in the two periods and in different physical activity strata using the Progetto CUORE risk score. RESULTS: Comparing the two studies, prevalence of OPA-low had decreased, whereas the prevalence of LTPA-low had increased. With increasing LTPA blood pressure, heart rate and glycemia decreased, whereas high-density lipoprotein-cholesterol increased with a positive effect on obesity, smoking habit and cardiovascular risk. CONCLUSIONS: Over the last 20 years, physical activity apparently changed: currently men and women dedicate more time to physical activity during leisure-time, and are less active at work. More active people have lower levels of major cardiovascular risk factors. Societal efforts are needed to increase physical activity levels in the population.

Adult↗

PubMed2005

Complete loss-of-function of the heart/muscle-specific adenine nucleotide translocator is associated with mitochondrial myopathy and cardiomyopathy.

Multiple mitochondrial DNA deletions are associated with clinically heterogeneous disorders transmitted as mendelian traits. Dominant missense mutations were found in the gene encoding the heart and skeletal muscle-specific isoform of the adenine nucleotide translocator (ANT1) in families with autosomal dominant progressive external opthalmoplegia and in a sporadic patient. We herein report on a sporadic patient who presented with hypertrophic cardiomyopathy, mild myopathy with exercise intolerance and lactic acidosis but no ophthalmoplegia. A muscle biopsy showed the presence of numerous ragged-red fibers, and Southern blot analysis disclosed multiple deletions of muscle mitochondrial DNA. Molecular analysis revealed a C to A homozygous mutation at nucleotide 368 of the ANT1 gene. The mutation converted a highly conserved alanine into an aspartic acid at codon 123 and was absent in 500 control individuals. This is the first report of a recessive mutation in the ANT1 gene. The clinical and biochemical features are different from those found in dominant ANT1 mutations, resembling those described in ANT1 knockout mice. No ATP uptake was measured in proteoliposomes reconstituted with protein extracts from the patient's muscle. The equivalent mutation in AAC2, the yeast ortholog of human ANT1, resulted in a complete loss of transport activity and in the inability to rescue the severe Oxidative Phosphorylation phenotype displayed by WB-12, an AAC1/AAC2 defective strain. Interestingly, exposure to reactive oxygen species (ROS) scavengers dramatically increased the viability of the WB-12 transformant, suggesting that increased redox stress is involved in the pathogenesis of the disease and that anti-ROS therapy may be beneficial to patients.

Adenine Nucleotide Translocator 1↗

PubMed2005

Prediction of coronary events in a low incidence population. Assessing accuracy of the CUORE Cohort Study prediction equation.

BACKGROUND: The aims of this paper are to derive a 10-year coronary risk predictive equation for adult Italian men, and to assess its accuracy in comparison with the Framingham Heart Study (FHS) and PROCAM study equations. METHODS: The CUORE study is a prospective fixed-cohort study. Eleven cohorts, from the north and the centre-south of Italy, had been investigated at baseline between 1982 and 1996, adopting MONICA methods to measure risk factors. Among this sample of 6865 men, aged 35-69 years and free of coronary heart disease (CHD) at baseline, 312 first fatal and non-fatal major coronary events occurred in 9.1 years median follow-up. Calibration, as the difference between 10-year predicted and actual risk, and discrimination, as the ability of the risk functions to separate high-risk from low-risk subjects, have been assessed to compare accuracy of the FHS, the PROCAM, and the CUORE study equations. RESULTS: The best CUORE equation includes age, total cholesterol, systolic blood pressure, cigarette smoking, HDL-cholesterol, diabetes mellitus, hypertension drug treatment, and family history of CHD (area under the ROC curve = 0.75). The uncalibrated estimates of the 10-year risk in this CUORE follow-up data were 0.093 and 0.109 higher (P < 0.05) from the Framingham and PROCAM risk scores, respectively, than the Kaplan-Meier estimate for CUORE, indicating risk overestimates for both equations. Standard recalibration techniques improved accuracy of the FHS equation only. PROCAM overestimates were prominent in the higher risk deciles. With an alternative method for recalibration better risk estimates were obtained, but a cohort study was needed to obtain a properly calibrated risk equation. CONCLUSIONS: The CUORE Project predictive equation showed better accuracy of the FHS and PROCAM equations, overcoming frequently reported risk overestimates. The CUORE equation may be adopted to identify men with high coronary risk in Italy.

Adult↗

PubMed2005

Age-related changes in cognitive domains. A population-based study.

BACKGROUND AND AIMS: The aim of the present study is to describe the effects of aging on various cognitive domains (global cognitive function, executive function, motor speed) in a population sample of elderly men, and to describe how their age-related changes are influenced by education, depression, or prevalent cerebrovascular accidents (CEVD). METHODS: A cross-sectional observational study was conducted in a cohort of 334 men, 65 to 95 years old, living in rural communities, participating in the Italian cohort of two population studies--MATISS (Malattie cardiovascolari ATerosclerotiche Istituto Superiore di Sanità) and FINE (Finland, Italy, Netherlands, Elderly). Global cognitive function was measured by the Mini-Mental State Examination (MMSE), executive function by the Stroop test, motor speed by the Purdue Pegboard test, and depression by the CES-D test. Prevalence of cerebrovascular accidents (CEVD), myocardial infarction, and diabetes were evaluated by a questionnaire and a clinical examination. Blood pressure, and total and HDL cholesterol were measured. Current smoking status was self-reported. RESULTS: An age-associated decline in global cognitive functions, executive functions, and motor speed was observed. The decline is more apparent after the age of 85 for the MMSE, and after 75 for executive functions and motor speed. Logistic regression analysis revealed that age was independently associated with altered global cognitive functions, executive functions, and motor speed, even after adjusting for education, depression or prevalent CEVD. CONCLUSIONS: In a cohort of community-living elderly men aged 65 to 95 years, age-associated changes in mental functions are more evident after the age of 85. These changes are independent of education, depression, or prevalent CEVD.

Aged↗

PubMed2005

Definition of high risk individuals to optimise strategies for primary prevention of cardiovascular diseases.

The identification of high risk individuals is one of the main goals of cardiovascular primary prevention and constitutes the basis for implementing actions oriented toward reducing modifiable risk factors at individual level, from changing life styles to drug interventions. The most appropriate method for identifying high risk individuals is the evaluation of their absolute global risk, a probability indicator of incidence, predictable on the basis of risk factor levels. Risk functions, derived from longitudinal studies, are used to identify persons at high probability to develop cardiovascular diseases. The appropriateness of the use of these risk functions depends upon the characteristics of the population that generated them and of individuals which they are applied to. Risk charts are simply absolute global risks calculated by classes of risk factors; risk scores are more precise evaluation derived from absolute global risks calculated by continuous levels of risk factors. Risk charts and scores are formed through the risk functions derived from different studies: Framingham, PROCAM (Munster), Seven Countries Study, SCORE and Progetto CUORE. A further chart has been created using the Framingham Study and adapted to the guidelines of New Zealand regarding the treatment of dyslipidemias and blood pressure. Major differences can be found in the availability of risk factors in men and women and in the use of fatal and non-fatal coronary and cerebrovascular events as end-points. All these studies use different diagnostic criteria for identification, classification and validation of events. The awareness of the risk charts differences is a key issue to refine tools for prevention of cardiovascular disease in populations with different probabilities of disease frequency.

Cardiovascular Diseases↗

PubMed2005

[Distribution of the global cardiovascular risk in the Italian population: results from the cardiovascular epidemiologic observatory].

BACKGROUND: The aim of this study was to assess the 10-year cardiovascular risk categories using risk chart, recently set up by the National Institute of Health in the population examined by the Cardiovascular Epidemiologic Observatory. METHODS: 3745 men and 3664 women aged 40-69 years were classified into five risk categories (< 5 %; 5-10%; 10-15%; 15-20%; > or = 20%) taking into account age, smoking habit, history of diabetes, systolic blood pressure, serum cholesterol and excluding those already under treatment for hypertension and hypercholesterolaemia or experienced a previous major cardiovascular event (1937 persons: 955 men, 982 women). RESULTS: Proportion of people estimated at risk in 10 years > or = 20% is minimal in the youngest age range, increases in adulthood, duplicates in smokers and is higher in diabetics. In non-diabetic men that proportion varies between 3.4% in non-smokers and 5.6% in smokers. All women at risk are already under specific treatment. CONCLUSIONS: Cardiovascular Epidemiologic Observatory data allowed to assess the expected proportion of individuals at risk in 10 years > or = 20%. Besides attention to high-risk individuals, preventive measures supporting a healthier lifestyle in the general population must be adopted, considering that it will produce the greatest number of events.

Adult↗

PubMed2004

Impaired mitochondrial glutamate transport in autosomal recessive neonatal myoclonic epilepsy.

Severe neonatal epilepsies with suppression-burst pattern are epileptic syndromes with either neonatal onset or onset during the first months of life. These disorders are characterized by a typical electroencephalogram pattern--namely, suppression burst, in which higher-voltage bursts of slow waves mixed with multifocal spikes alternate with isoelectric suppression phases. Here, we report the genetic mapping of an autosomal recessive form of this condition to chromosome 11p15.5 and the identification of a missense mutation (p.Pro206Leu) in the gene encoding one of the two mitochondrial glutamate/H(+) symporters (SLC25A22, also known as "GC1"). The mutation cosegregated with the disease and altered a highly conserved amino acid. Functional analyses showed that glutamate oxidation in cultured skin fibroblasts from patients was strongly defective. Further studies in reconstituted proteoliposomes showed defective [(14)C]glutamate uniport and [(14)C]glutamate/glutamate exchange by mutant protein. Moreover, expression studies showed that, during human development, SLC25A22 is specifically expressed in the brain, within territories proposed to contribute to the genesis and control of myoclonic seizures. These findings provide the first direct molecular link between glutamate mitochondrial metabolism and myoclonic epilepsy and suggest potential insights into the pathophysiological bases of severe neonatal epilepsies with suppression-burst pattern.

Amino Acid Transport System X-AG↗

PubMed2004

The yeast peroxisomal adenine nucleotide transporter: characterization of two transport modes and involvement in DeltapH formation across peroxisomal membranes.

The yeast peroxisomal adenine nucleotide carrier, Ant1p, was shown to catalyse unidirectional transport in addition to exchange of substrates. In both transport modes, proton movement occurs. Nucleotide hetero-exchange is H+-compensated and electroneutral. Furthermore, microscopic fluorescence imaging of a pH-sensitive green fluorescent protein targeted to peroxisomes shows that Ant1p is involved in the formation of a DeltapH across the peroxisomal membrane, acidic inside.

Adenine Nucleotides↗

PubMed2004

Identification of the mitochondrial ATP-Mg/Pi transporter. Bacterial expression, reconstitution, functional characterization, and tissue distribution.

The mitochondrial carriers are a family of transport proteins that, with a few exceptions, are found in the inner membranes of mitochondria. They shuttle metabolites, nucleotides, and cofactors through this membrane and thereby connect and/or regulate cytoplasm and matrix functions. ATP-Mg is transported in exchange for phosphate, but no protein has ever been associated with this activity. We have isolated three human cDNAs that encode proteins of 458, 468, and 489 amino acids with 66-75% similarity and with the characteristic features of the mitochondrial carrier family in their C-terminal domains and three EF-hand Ca(2+)-binding motifs in their N-terminal domains. These proteins have been overexpressed in Escherichia coli and reconstituted into phospholipid vesicles. Their transport properties and their targeting to mitochondria demonstrate that they are isoforms of the ATP-Mg/Pi carrier described in the past in whole mitochondria. The tissue specificity of the three isoforms shows that at least one isoform was present in all of the tissues investigated. Because phosphate recycles via the phosphate carrier in mitochondria, the three isoforms of the ATP-Mg/Pi carrier are most likely responsible for the net uptake or efflux of adenine nucleotides into or from the mitochondria and hence for the variation in the matrix adenine nucleotide content, which has been found to change in many physiopathological situations.

Adenosine Triphosphate↗

PubMed2004

Mutations in AAC2, equivalent to human adPEO-associated ANT1 mutations, lead to defective oxidative phosphorylation in Saccharomyces cerevisiae and affect mitochondrial DNA stability.

Autosomal dominant and recessive forms of progressive external ophthalmoplegia (adPEO and arPEO) are mitochondrial disorders characterized by the presence of multiple deletions of mitochondrial DNA in affected tissues. Four adPEO-associated missense mutations have been identified in the ANT1 gene. In order to investigate their functional consequences on cellular physiology, we introduced three of them at equivalent positions in AAC2, the yeast orthologue of human ANT1. We demonstrate here that expression of the equivalent mutations in aac2-defective haploid strains of Saccharomyces cerevisiae results in (a) a marked growth defect on non-fermentable carbon sources, and (b) a concurrent reduction of the amount of mitochondrial cytochromes, cytochrome c oxidase activity and cellular respiration. The efficiency of ATP and ADP transport was variably affected by the different AAC2 mutations. However, irrespective of the absolute level of activity, the AAC2 pathogenic mutants showed a significant defect in ADP versus ATP transport compared with wild-type AAC2. In order to study whether a dominant phenotype, as in humans, could be observed, the aac2 mutant alleles were also inserted in combination with the endogenous wild-type AAC2 gene. The heteroallelic strains behaved as recessive for oxidative growth and petite-negative phenotype. In contrast, reduction in cytochrome content and increased mtDNA instability appeared to behave as dominant traits in heteroallelic strains. Our results indicate that S. cerevisiae is a suitable in vivo model to study the pathogenicity of the human ANT1 mutations and the pathophysiology leading to impairment of oxidative phosphorylation and damage of mtDNA integrity, as found in adPEO.

Adenine Nucleotide Translocator 1↗

PubMed2004

Identification of the mitochondrial GTP/GDP transporter in Saccharomyces cerevisiae.

The genome of Saccharomyces cerevisiae contains 35 members of a family of transport proteins that, with a single exception, are found in the inner membranes of mitochondria. The transport functions of the 16 biochemically identified mitochondrial carriers are concerned with shuttling substrates, biosynthetic intermediates, and cofactors across the inner membrane. Here the identification and functional characterization of the mitochondrial GTP/GDP carrier (Ggc1p) is described. The ggc1 gene was overexpressed in bacteria. The purified protein was reconstituted into liposomes, and its transport properties and kinetic parameters were characterized. It transported GTP and GDP and, to a lesser extent, the corresponding deoxynucleotides and the structurally related ITP and IDP by a counter-exchange mechanism. Transport was saturable with an apparent K(m) of 1 microm for GTP and 5 microm for GDP. It was strongly inhibited by pyridoxal 5'-phosphate, bathophenanthroline, tannic acid, and bromcresol purple but little affected by the inhibitors of the ADP/ATP carrier carboxyatractyloside and bongkrekate. Furthermore, in contrast to the ADP/ATP carrier, the Ggc1p-mediated GTP/GDP heteroexchange is H(+)-compensated and thus electroneutral. Cells lacking the ggc1 gene had reduced levels of GTP and increased levels of GDP in their mitochondria. Furthermore, the knock-out of ggc1 results in lack of growth on nonfermentable carbon sources and complete loss of mitochondrial DNA. The physiological role of Ggc1p in S. cerevisiae is probably to transport GTP into mitochondria, where it is required for important processes such as nucleic acid and protein synthesis, in exchange for intramitochondrially generated GDP.

Cloning, Molecular↗