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R Erdmann

Publications and source records attributed to R Erdmann.

At least 37 records · Page 2Linked to original sources
PubMed1998

IDP3 encodes a peroxisomal NADP-dependent isocitrate dehydrogenase required for the beta-oxidation of unsaturated fatty acids.

In Saccharomyces cerevisiae the metabolic degradation of saturated fatty acids is exclusively confined to peroxisomes. In addition to a functional beta-oxidation system, the degradation of unsaturated fatty acids requires auxiliary enzymes, including a Delta2, Delta3-enoyl-CoA isomerase and an NADPH-dependent 2,4-dienoyl-CoA reductase. We found both enzymes to be present in yeast peroxisomes. The impermeability of the peroxisomal membrane for pyrimidine nucleotides led to the question of how the NADPH needed by the reductase is regenerated in the peroxisomal lumen. We report the identification and functional analysis of the IDP3 gene product, which is a yeast peroxisomal NADP-dependent isocitrate dehydrogenase. The newly identified peroxisomal protein is homologous to the mitochondrial Idp1p and cytosolic Idp2p, which both are yeast NADP-dependent isocitrate dehydrogenases. Yeast cells lacking Idp3p grow normally on saturated fatty acids, but growth is impaired on unsaturated fatty acids, indicating that the peroxisomal Idp3p is involved in their metabolic utilization. The data presented are consistent with the assumption that peroxisomes of S. cerevisiae contain the enzyme equipment needed for the degradation of unsaturated fatty acids, including an NADP-dependent isocitrate dehydrogenase, a putative constituent of a peroxisomal NADPH-regenerating redox system.

Amino Acid Sequence↗
PubMed1998

Pex19p, a farnesylated protein essential for peroxisome biogenesis.

We report the identification and molecular characterization of Pex19p, an oleic acid-inducible, farnesylated protein of 39.7 kDa that is essential for peroxisome biogenesis in Saccharomyces cerevisiae. Cells lacking Pex19p are characterized by the absence of morphologically detectable peroxisomes and mislocalization of peroxisomal matrix proteins to the cytosol. The human HK33 gene product was identified as the putative human ortholog of Pex19p. Evidence is provided that farnesylation of Pex19p takes place at the cysteine of the C-terminal CKQQ amino acid sequence. Farnesylation of Pex19p was shown to be essential for the proper function of the protein in peroxisome biogenesis. Pex19p was shown to interact with Pex3p in vivo, and this interaction required farnesylation of Pex19p.

Amino Acid Sequence↗
PubMed1997

Pex14p, a peroxisomal membrane protein binding both receptors of the two PTS-dependent import pathways.

Pex14p, an S. cerevisiae peroxin, is attached to the outer face of the peroxisomal membrane and is a component of the protein import machinery. Pex14p interacts with both the PTS1 and PTS2 receptors. It is the only known peroxisomal membrane protein that binds the PTS2 receptor and might thus mediate the membrane docking event of PTS2-dependent protein import. These results suggest that the two import pathways overlap and, furthermore, that Pex14p represents the point of convergence. Pex14p also interacts with two other membrane-bound peroxins including Pex13p, another binding protein for the PTS1 receptor. The data presented here are consistent with the idea of a common translocation machinery for both PTS-dependent protein import pathways in the peroxisomal membrane.

Biological Transport↗
PubMed1997

Exercise capacity during and after spaceflight.

UNLABELLED: Our aim was to elucidate why astronaut's exercise capacity after spaceflight is reduced. Therefore, the kinetics of oxygen uptake (VO2) as a measure for muscular aerobic capacity, as well as maximal oxygen uptake (VO2peak), and anaerobic threshold (PAT) as overall measures for exercise capacity were determined. Measurements of VO2peak and AT were restricted to pre- and postflight sessions. METHODS: Four crew-members of the D-2 mission (10 d) were cycling with steady state phases at 20 W and 80 W, followed by 450s of pseudo random binary sequence (PRBS) changes between 20 W and 80 W, and an incremental exercise test (10 W every 30 s) up to subjective exhaustion. Breath-by-breath VO2, VCO2, ventilation, HR, and blood pressure were continuously recorded. Blood lactate samples were drawn only during the incremental phase. The VO2 kinetics were determined by evaluation of the relationship between the workload and the instantaneous oxygen uptake of each subject. The cross-correlation function between both variables showed two characteristic items, the maximum as a measure for the muscular aerobic capacity, and its lag representing time consuming processes. RESULTS AND DISCUSSION: Each subject showed an individual characteristic of VO2 kinetics. In flight, no significant changes were detected compared to preflight data. Decreases in lags of cross-correlation function maxima and decreases in mean blood pressure during exercise indicate lowered blood volumes 2 d after the flight. Lowered blood volumes can explain the losses in exercise capacity. The maximum of the cross-correlation function did not change significantly which indicates unchanged muscular oxidative capacity.

Adult↗
PubMed1996

Identification of a yeast peroxisomal member of the family of AMP-binding proteins.

We established a reverse-genetic approach to identify peroxisomal proteins involved in peroxisomal fatty acid metabolism of Saccharomyces cerevisiae. Putative peroxisomal peripheral membrane proteins were isolated by successive extraction of purified peroxisomes and purified by HPLC and SDS/PAGE. Six proteins were identified by peptide sequence analysis, including acyl-CoA oxidase and a trifunctional enzyme of the peroxisomal beta-oxidation system as well as peroxisomal malate dehydrogenase 3 and carnitine acetyltransferase. In addition two previously unknown putative peroxisomal proteins were identified, an unknown 40-kDa protein and a protein which we named Pcs60p, both major constituent of the isolated protein fraction. Pcs60p is encoded by ORF Z36091 of chromosome II from S. cerevisiae and consists of 543 amino acids with a molecular mass of 60.5 kDa. Biochemical, immunofluorescence microscopy and immunocytochemical data confirmed that Pcs60p is a peroxisomal peripheral membrane protein but the protein is also localized in the peroxisomal matrix. Consistent with the intraperoxisomal localization, the consensus sequence for a peroxisomal-targeting signal 1 (PTS1) is present at the extreme C-terminus of Pcs60p. Deletion studies revealed that the peroxisomal localization of the protein depends on the presence of this signal sequence. Expression of Pcs60p is highly inducible by oleic acid, however, the protein is dispensable for growth on oleic acid as single carbon source. Pcs60p belongs to the family of proteins which act via an ATP-dependent covalent binding of AMP to their substrates and shows the highest degree of similarity to the Escherichia coli long chain acyl-CoA synthetase.

Adenosine Monophosphate↗
PubMed1996

[Nicotine in neuropsychiatric movement disorders].

Nicotine has various effects in the CNS, especially in dopaminergic and cholinergic systems, relevant in pathophysiology of neuropsychiatric movement disorders. Nicotine acutely reduce the symptomatology in Parkinson's disease. In neuroleptic-induced Parkinsonism (NIP) acute nicotine application induces positive changes of symptomatology. Chronic application, however, leads to a greater likelihood of NIP. The results concerning tardive dyskinesia are not consistent, but nicotine tends to exercise a positive influence on basic mechanisms. In the Gilles-de-la-Tourette syndrome nicotine reduces the severity and frequency of the tics given in combination with haloperidol.

Adult↗
PubMed1996

Identification of Pex13p a peroxisomal membrane receptor for the PTS1 recognition factor.

We have identified an S. cerevisiae integral peroxisomal membrane protein of M of 42,705 (Pex13p) that is a component of the peroxisomal protein import apparatus. Pex13p's most striking feature is an src homology 3 (SH3) domain that interacts directly with yeast Pex5p (former Pas10p), the recognition factor for the COOH-terminal tripeptide signal sequence (PTS1), but not with Pex7p (former Pas7p), the recognition factor for the NH2-terminal nonapeptide signal (PTS2) of peroxisomal matrix proteins. Hence, Pex13p serves as peroxisomal membrane receptor for at least one of the two peroxisomal signal recognition factors. Cells deficient in Pex13p are unable to import peroxisomal matrix proteins containing PTS1 and, surprisingly, also those containing PTS2. Pex13p deficient cells retain membranes containing the peroxisomal membrane protein Pex11p (former Pmp27p), consistent with the existence of independent pathways for the integration of peroxisomal membrane proteins and for the translocation of peroxisomal matrix proteins.

Acetyl-CoA C-Acetyltransferase↗
PubMed1995

Giant peroxisomes in oleic acid-induced Saccharomyces cerevisiae lacking the peroxisomal membrane protein Pmp27p.

We have purified peroxisomal membranes from Saccharomyces cerevisiae after induction of peroxisomes in oleic acid-containing media. About 30 distinct proteins could be discerned among the HPLC- and SDS-PAGE-separated proteins of the high salt-extracted peroxisomal membranes. The most abundant of these, Pmp27p, was purified and the corresponding gene PMP27 was cloned and sequenced. Its primary structure is 32% identical to PMP31 and PMP32 of the yeast Candida biodinii (Moreno, M., R. Lark, K. L. Campbell, and M. J. Goodman. 1994. Yeast. 10:1447-1457). Immunoelectron microscopic localization of Pmp27p showed labeling of the peroxisomal membrane, but also of matrix-less and matrix containing tubular membranes nearby. Electronmicroscopical data suggest that some of these tubular extensions might interconnect peroxisomes to form a peroxisomal reticulum. Cells with a disrupted PMP27 gene (delta pmp27) still grew well on glucose or ethanol, but they failed to grow on oleate although peroxisomes were still induced by transfer to oleate-containing media. The induced peroxisomes of delta pmp27 cells were fewer but considerably larger than those of wild-type cells, suggesting that Pmp27p may be involved in parceling of peroxisomes into regular quanta. delta pmp27 cells cultured in oleate-containing media form multiple buds, of which virtually all are peroxisome deficient. The growth defect of delta pmp27 cells on oleic acid appears to result from the inability to segregate the giant peroxisomes to daughter cells.

ATP-Binding Cassette Transporters↗
PubMed1995

[Bromine poisoning].

Intoxication by medication containing bromid has become so rare in recent years, that the clinical syndrome is nearly forgotten. The revival of brom in neurology at present points to an increased rate of bromintoxications. With this background and a corresponding case-history the symptoms and therapy of bromintoxication is represented.

Adult↗
PubMed1995

[Neuroleptics and nicotine].

Excessive smoking is a well know phenomenon in psychiatry. Nicotine, the most important content of cigarette tobacco, interacts with several receptors of neurotransmitters in the CNS: especially the dopaminergic system appears to be relevant in this respect. Nicotine is a potent substance to counteract neuroleptic-induced parkinsonism. On the other hand nicotine is possibly a risk-factor for tardive dyskinesia. Nicotine has enormous therapeutical implications.

Antipsychotic Agents↗
PubMed1994

PAS7 encodes a novel yeast member of the WD-40 protein family essential for import of 3-oxoacyl-CoA thiolase, a PTS2-containing protein, into peroxisomes.

To identify components of the peroxisomal import pathway in yeast, we have isolated pas mutants affected in peroxisome biogenesis. Two mutants assigned to complementation group 7 define a new gene, PAS7, whose product is necessary for import of thiolase, a PTS2-containing protein, but not for that of SKL (PTS1)-containing proteins, into peroxisomes. We have cloned PAS7 by complementation of the oleic acid non-utilizing phenotype of the pas7-1 strain. The DNA sequence predicts a 42.3 kDa polypeptide of 375 amino acids encoding a novel member of the beta-transducin related (WD-40) protein family. A Myc epitope-tagged Pas7p, expressed under the control of the CUP1 promotor, was functionally active. Subcellular localization studies revealed that in the presence of thiolase this epitope-tagged Pas7p in part associates with peroxisomes. However, in a thiolase-deficient mutant, Pas7p was entirely found in the cytoplasm. We suggest that Pas7p mediates the binding of thiolase to these organelles.

Acetyl-CoA C-Acyltransferase↗
PubMed1994

The 2.8 A crystal structure of peroxisomal 3-ketoacyl-CoA thiolase of Saccharomyces cerevisiae: a five-layered alpha beta alpha beta alpha structure constructed from two core domains of identical topology.

BACKGROUND: The peroxisomal enzyme 3-ketoacyl-coenzyme A thiolase of the yeast Saccharomyces cerevisiae is a homodimer with 417 residues per subunit. It is synthesized in the cytosol and subsequently imported into the peroxisome where it catalyzes the last step of the beta-oxidation pathway. We have determined the structure of this thiolase in order to study the reaction mechanism, quaternary associations and intracellular targeting of thiolases generally, and to understand the structural basis of genetic disorders associated with human thiolases. RESULTS: Here we report the crystal structure of unliganded yeast thiolase refined at 2.8 A resolution. The enzyme comprises three domains; two compact core domains having the same fold and a loop domain. Each of the two core domains is folded into a mixed five-stranded beta-sheet covered on each side by helices and the two are assembled into a five-layered alpha beta alpha beta alpha structure. The central layer is formed by two helices, which point with their amino termini towards the active site. The loop domain, which is to some extent stabilized by interactions with the other subunit, runs over the surface of the two core domains, encircling the active site of its own subunit. CONCLUSIONS: The crystal structure of thiolase shows that the active site is a shallow pocket, shaped by highly conserved residues. Two conserved cysteines and a histidine at the floor of this pocket probably play key roles in the reaction mechanism. The two active sites are on the same face of the dimer, far from the amino and carboxyl termini of both subunits and the disordered amino-terminal import signal sequence.

Acetyl-CoA C-Acyltransferase↗
PubMed1994

The peroxisomal targeting signal of 3-oxoacyl-CoA thiolase from Saccharomyces cerevisiae.

All peroxisomal 3-oxoacyl-CoA thiolases identified so far do not contain the previously identified tripeptide peroxisomal targeting signal at their carboxy-termini. For the two rat thiolases it was shown that their peroxisomal targeting signals are localized within the amino-terminal region of the proteins and are cleaved upon import. This report demonstrates that the N-terminal region of the peroxisomal 3-oxoacyl-CoA thiolase from Saccharomyces cerevisiae is essential for its peroxisomal targeting, and that the N-terminal 16 amino acids of yeast thiolase are sufficient to target the otherwise cytosolic small subunit of ribulose-1,5-bisphosphate carboxylase to peroxisomes for import.

Acetyl-CoA C-Acetyltransferase↗
PubMed1994

Purification and immunolocalization of the peroxisomal 3-oxoacyl-CoA thiolase from Saccharomyces cerevisiae.

A molecular understanding of peroxisome biogenesis depends upon the analysis of peroxisomal proteins. Here we describe the isolation of the 3-oxoacyl-CoA thiolase of the peroxisomal beta-oxidation system from Saccharomyces cerevisiae as a dimer of identical subunits, each with a molecular mass of 45 kDa. Monospecific polyclonal antibodies were raised against the purified enzyme, and its peroxisomal origin was demonstrated by immunoblotting of subcellular fractions as well as by immunogold labelling. We also show that these antibodies could be suitable for an immunofluorescence microscopy screening of yeast mutants affected in peroxisome assembly.

Acetyl-CoA C-Acyltransferase↗
PubMed1994

Effect of site-directed mutagenesis of conserved lysine residues upon Pas1 protein function in peroxisome biogenesis.

The Pas1 protein (Pas1p) is required for peroxisome biogenesis in Saccharomyces cerevisiae and contains two putative ATP-binding sites, each within a domain which is conserved among members of the recently characterized AAA-family. To elucidate whether both putative ATP-binding sites are essential for Pas1p function, lysine 467 of the first and lysine 744 of the second putative ATP-binding site were each changed to glutamate by site-directed mutagenesis. While replacement of lysine 744 abolished the function of the Pas1 protein in peroxisome biogenesis, replacement of lysine 467 had no obvious effect.

ATPases Associated with Diverse Cellular Activitie↗