Schizosaccharomyces pombe gene GHT1 is highly homologous to other prokaryotic, yeast and higher eukaryotic genes coding for monosaccharide transporters.
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Amino Acid Sequence↗
Biomedical subjects
M Höfer
Publications and source records attributed to M Höfer.
The SpTRK gene encodes a potassium-specific transport protein TKHp in Schizosaccharomyces pombe.
Complementary DNAs involved in potassium transport in Schizosaccharomyces pombe were selected by complementation of defective K+ uptake in a trk1 trk2 mutant of Saccharomyces cerevisiae. Here we describe the SpTRK gene that encodes a protein of 833 amino acids. The predicted structure contains 12 putative membrane-spanning domains and resembles various high- and low-affinity systems for K+ transport in yeasts and plants. TKHp, the product of SpTRK exhibits high homology to TRK1 and TRK2 of Saccharomyces cerevisiae as well as to HKT1 of Triticum aestivum, but is not related to HAK1 of another ascomycete, Schwanniomyces occidentalis, suggesting that different routes for potassium uptake evolved independently. This protein is a potassium-specific transporter since functional analysis of the SpTRK complemented mutant strain of Sacch. cerevisiae revealed potassium transport affinities and uptake characteristics similar to those obtained in wild-type Sch. pombe. Patch-clamp analysis in the whole-cell mode confirmed the TKHp-mediated inward current in the complemented strain. The inward current increased by acidification of the extracellular medium thereby suggesting a mechanism of K+H+ cotransport. The inward current is not detectable when external K+ is substituted by Na+, documenting a distinct cation specificity of the protein.
Amino Acid Sequence↗
[Pancreatoblastoma--a rare pancreatic malignancy in childhood].
Between 1885 and 1991 only 71 cases of malignant pancreatic tumours in childhood and adolescence have been reported in literature; the majority of these were pancreatoblastomas. The symptoms, pathology and therapy of this rare tumour are demonstrated in the case of a 17-year-old girl. The tumour is believed to develop at an early stage of pancreatic cell differentiation. Usually it is composed of both exocrine and endocrine cell types. The treatment of choice is radical resection. In contrast to pancreatic neoplasms in adult patients the pancreatoblastoma has a favourable prognosis. The role of adjuvant chemotherapy or radiotherapy is still under discussion due to the small number of patients treated as yet.
Adolescent↗
Intensity of electron channeling radiation, and occupation lengths in diamond crystals.
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Journal Article↗
Glucose-transport-deficient mutants of Schizosaccharomyces pombe: phenotype, genetics and use for genetic complementation.
Glucose-transport-deficient mutants of Schizosaccharomyces pombe were obtained by treatment of wild-type cells (972h-) with N-methyl-N'-nitro-N- nitrosoguanidine, and by selection of resulting mutants on gluconate medium containing 0.05% 2-deoxy-D-glucose (2DG). One mutant, designated YGS-B22, was unable to grow on D-glucose and/or D-fructose as a carbon source (Glc/Fru-), and was resistant to 2DG; hence, none of the three sugars was taken up by the mutant cells. The hexokinase activity in the wild-type and the mutant cells was equal. Genetic purification of YGS-B22 by back-crossing with a leucine-auxotrophic mutant and the wild-type resulted in two strains: YGS-4, with reduced 2DG resistance, and YGS-5, which had lost 2DG-resistance. YGS-5 grew in D-glucose-containing media, albeit very slowly. No measurable sugar uptake was detectable in either of the two mutants within the 1 h test interval. Tetrad analyses proved a Mendelian segregation of growth on D-glucose and leucine auxotrophy. However, 2DG resistance did not co-segregate with the Glc/Fru- phenotype, indicating that the transport deficiency and 2DG resistance characters are not encoded on the same genomic locus. Using a genomic bank of Sch. pombe, two transformants, YGS-5-G7 and YGS-5-G12, were found which had regained the wild-type growth and transport phenotype by complementation. Correspondingly, both D-glucose uptake and 2DG accumulation were restored in the transformed strains.(ABSTRACT TRUNCATED AT 250 WORDS)
Biological Transport↗
Ionic channels in the plasma membrane of Schizosaccharomyces pombe: evidence from patch-clamp measurements.
Patch-clamp studies of the yeast Schizosaccharomyces pombe reveal that the plasma membrane contains a voltage-gated channel mildly selective for potassium over sodium, lithium, and chloride. The channel exhibits several conductances with a maximum of 153 pS. The channel gates in the region of physiologically relevant voltages, being closed at hyperpolarizing and open at depolarizing voltages. It is not inhibited by tetraethylammonium, quinine, or quinidine applied from the cytoplasmic side of the membrane; similarly, ATP and stretch have no effect. The frequency of its occurrence in patches implies that about 35 channels of this kind are present in the plasma membrane of a single cell.
Adenosine Triphosphate↗
Effect of hydrogen peroxide on sugar transport in Schizosaccharomyces pombe. Absence of membrane lipid peroxidation.
Stationary unaerated cells of S. pombe containing endogenous substrates but not energized by any exogenous ones take up 2-deoxy-D-glucose, 6-deoxy-D-glucose, D-xylose and D-arabinose actively over diffusion equilibrium. The active uptake is inhibited by 20-100 mmol/L H2O2 which causes an increase in KT but has no effect on Jmax. This "competitive inhibition" indicates that H2O2 affects directly the sugar binding sites of the transporters. The ATP-binding site of the plasma membrane H(+)-ATPase is also affected by 100 mmol/L H2O2; the KT decreases 7-fold, Jmax about 2.5-fold. These effects are not likely to be mediated by membrane lipid peroxidation which appears to be lacking in S. pombe, and this lack may be one of the reasons for the high resistance of this yeast to H2O2. Because of this S. pombe represents a suitable system for studying direct effects of oxidants on membrane proteins.
Antimycin A↗
Response of catalase activity and membrane fluidity of aerobically grown Schizosaccharomyces pombe and Saccharomyces cerevisiae to aeration and the presence of substrates.
Intracellular catalase (EC 1.11.1.6) activity of permeabilized aerobically grown cells of Schizosaccharomyces pombe was insensitive to cell aeration and inhibition of protein synthesis, and was only mildly enhanced by the presence of glucose and ethanol via de novo protein synthesis. By contrast, the intracellular catalase activity of Saccharomyces cerevisiae, which, in freshly harvested cells, was two to three times lower than that in Sch. pombe, increased on aeration without substrates or with ethanol and was inhibited on aeration with glucose following cell permeabilization. The enhanced intracellular activity was due to de novo protein synthesis while the inhibitory effect of glucose, absent in Sch. pombe, was caused by one of the major glucose metabolites, succinate. The intact-cell catalase activity of both yeasts increased greatly during aeration. In Sacch. cerevisiae, this increase was again prevented by glucose. In parallel, export of catalase to the cell surface increased in both yeasts. This was especially conspicuous in Sch. pombe aerated in the presence of ethanol, and may represent a protective mechanism against the damaging effects of ethanol. The cell-surface-bound catalase activity was confirmed in isolated plasma membranes of both yeasts. The fluidity of the plasma membrane increased during aeration. This effect was further stimulated by the presence of glucose and to a lesser extent by ethanol. Both yeasts exhibited increased extracellular catalase activity during aeration which could not be caused entirely by cell lysis. In Sch. pombe this activity was strongly enhanced by the presence of ethanol.
Aerobiosis↗
Mechanisms of acid extrusion in yeast.
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Acid-Base Equilibrium↗
Activation of the plasma membrane H(+)-ATPase of Saccharomyces cerevisiae by addition of hydrogen peroxide.
Addition of hydrogen peroxide (greater than 10 mM) to aerated derepressed cells of S. cerevisiae in the absence of substrate caused a boost of endogenous respiration and both intra- and extracellular acidification, without any significant change in cellular ATP level. Furthermore, a hyperpolarization of the plasma membrane was indicated by an enhanced accumulation of tetraphenylphosphonium in the cells. The extracellular pH attained was as low as 3.5. The acidification could be suspended by the H(+)-ATPase inhibitors diethylstilbestrol and dicyclohexylcarbodiimide and was, in general, associated with an opposite flux of K+. K+ also stimulated the H(+)-ATPase activity in the purified plasma membrane fraction. These results are consistent with the plasma membrane H(+)-ATPase being involved in the H+ extrusion induced by H2O2 in the absence of substrate. Extended exposure of cells to H2O2 led eventually to an arrest of both respiration and ion fluxes that could be again lifted by depolarizing the plasma membrane. Along with differences in the cellular NADH/NAD+ ratio and in the participation of organic acids, this makes the H2O2-induced acidification distinct from that induced by glucose.
Buffers↗
Anti-sense RNA efficiently inhibits formation of the 10 kd polypeptide of photosystem II in transgenic potato plants: analysis of the role of the 10 kd protein.
A chimeric gene encoding an anti-sense RNA of the 10 kd protein of the water-splitting apparatus of photosystem II of higher plants under the control of the CaMV 35S promoter was introduced into potato using Agrobacterium based vectors. The expression of the anti-sense RNA led to a significant reduction of the amounts of the 10 kd protein and RNA in a number of transgenic plants. In three out of 36 plants tested, the level of the 10 kd protein was only up to 1-3% compared with the wild-type control. The drastic reduction of the 10 kd protein did not influence the accumulation of other photosystem II associated polypeptides at both the RNA and protein level. Furthermore no phenotypic differences were observed between potato plants expressing wild-type and drastically reduced levels of the 10 kd protein with respect to growth rate, habitus or ultrastructure of the chloroplasts. Measurements of the relaxation of the flash-induced enhancement in the fluorescence quantum yield as determined in intact leaves and the rates and characteristic oscillation pattern of O2 evolution as determined in isolated thylakoid samples however, show that the elimination of the 10 kd protein on the one hand retards reoxidation of QA- and on the other hand introduces a general disorder into the PSII complex.
Blotting, Western↗
Analysis of the H+/sugar symport in yeast under conditions of depolarized plasma membrane.
H+/sugar symport in the obligatory aerobic yeast Rhodotorula glutinis was analyzed under conditions where the plasma membrane was selectively depolarized by the lipophilic cation tetraphenylphosphonium (TPP+). Control experiments showed that this treatment did not impair the transmembrane delta pH, the cell energy charge, and the function of plasma membrane H+-ATPase. The kinetic data were fitted to elementary functions derived from a model constructed on the basis of some simplifying premises for ordered (either C + H+ + S or C + S + H+) and random reaction mechanisms. In addition, the comparison of the kinetic parameters in fully energized and depolarized cells provided information about the free carrier charge. It was concluded that the binding sequence of formation of the ternary carrier/H+/substrate complex follows a random mechanism and that the carrier bears a negative charge.
Biological Transport, Active↗
[Comparative studies of the suitability of different culture media for the isolation of Mycoplasma californicum from milk samples].
Mycoplasma (M.) californicum und M. bovigenitalium mastitis had occurred in four herds. 240 milk samples of 120 cows were tested for M. californicum, using in parallel nine different culturing substrates and test methods. Included were 120 initial and 120 final milk samples. Inoculation of milk to medium-I broth containing V-factor yeast extract, incubation at 37 degrees C for 5 days, subsequent spreading onto cattle blood agar with staphylococcal nutrix, followed by 5 days of incubation proved to be superior to all other culturing substrates and methods tested and resulted in positive detection of M. californicum in 69 milk samples. M. californicum was identified in 70 milk samples by combination of all 9 test variants. No significant difference was found to exist with regard to isolation results between initial and final milking samples.
Animals↗
[Doppler sonography of testicular circulation following reconstruction of inguinal hernia].
The use of pre- and postoperative testicular Doppler ultrasound examination in groin hernia repair is evaluated in 50 patients operated by the technique of Shouldice. The etiological differentiation between ischemic orchitis and testicular necrosis is based on the monitoring of testicular perfusion. The technique is presented in detail. Preoperatively the arterial supply could be examined in 45 of 50 patients and the venous flow in 41 patients. The postoperative arterial flow was found in all and the venous flow in 47 patients. Our results revealed the Doppler sonography as a suitable technique for postoperative semiquantitative examination of testicular perfusion. It should be employed in all cases of postoperative testicular pain. A mandatory use of the Doppler technique to obtain an indication for operative revision has still to be discussed.
Adult↗
[Tuberculosis following liver transplantation].
Seven months after orthotopic liver transplantation because of terminal postnecrotic cirrhosis, a 55-year-old patient was found to have pulmonary tuberculosis with fever, cough and an infiltration in the left upper lobe. Sputum culture grew M. Tuberculosis. He received ethambutol (1.6 g/d) and isoniazid (400 mg three times weekly, after 1 1/2 months 200 mg thrice weekly). After eleven months the tuberculosis had healed with only minor residua. The function of the transplant was very good in the fourth year after the operation. The main side effect was a reversible rise in liver enzymes. If possible, patients should not be given hepatotoxic tuberculostatic agents after liver transplantation, in no circumstances rifampicin. Dosage should be adapted to the liver function so as to avoid damage to transplant function.
Antitubercular Agents↗
Significance of thymus differential ratio in immunologic status of graft tolerance.
LEW with BDE-heart graft received 0 (control), 15, or 40 mg cyclosporine (CsA)/kg b. wt. per day. On postoperative days 3, 5, 7, 10, and 14 in four animals each weight and cell count of thymus and spleen were determined, and thymus and spleen cell subpopulations were examined with monoclonal antibodies. The same tests were performed in FiS heart graft recipients without immunosuppression and ungrafted LEW which received 15 or 40 mg CsA. We expressed alterations in thymocyte subpopulations by using the differentiation ratio (DR), i.e., differentiated in % of all T-cells and by the ratio of helper to suppressor/cytotoxic T-cells (Th-Ts/c). In graft rejection the thymus showed no significant change in DR or Th-Ts/c. However, in the CsA-induced graft tolerance DR was elevated and at the same time Th-Ts/c declined, both showing maximum values on days 5 and 7 and a return to normal thereafter. FiS graft recipients exhibited similar thymus alterations as tolerant recipients, but less marked. In CsA-treated ungrafted LEW, elevation of DR was slight after 15 mg but very strong after 40 mg CsA (93% on day 7), and it did not return to normal in the latter group. Th-Ts/c was decreased in these ungrafted animals, but not as strongly as in tolerant graft recipients. Such thymus alterations were not observed in graft rejection. Spleen weights were strongly increased in graft rejection and unchanged in graft tolerance. Splenic Ts/c and Th-Ts/s were increased in CsA-treated tolerant recipients but not in graft rejection. We conclude that elevation of DR and decline of thymic Th-Ts/c in the initial postoperative phase are indicators of graft tolerance in organ recipients.
Animals↗
[Ulrich and Ulrich oculo-oscillodynamography: results in patients with healthy eyes].
Ulrich and Ulrich's method of oculo-oscillodynamography (OODG) is a relatively new method which enables the systolic retinal, systolic ciliary, and systolic ocular perfusion pressure or respectively blood pressure to be measured. The results obtained by the present authors are in good agreement with those of Ulrich and Ulrich (n = 30). The intraocular pressure values obtained with this method correlate somewhat less well with the systemic blood pressure than is the case with suction cup ophthalmodynamometry. However, the correlation coefficients are sufficiently high to permit their application in ophthalmological diagnosis. The results presented here indicate that the diastolic ocular pressure should be determined by applying the formoscillatory criterion. The positive intercept in the regression equations can be explained by the assumption that the regression is curvilinear at systemic blood pressure values which are generally not encountered in humans in whom OODG is of diagnostic importance. It is suggested that the linear regression is a sufficiently exact model at the systemic blood pressures most frequently measured. Normal OODG values can be read off easily from the diagrams published here.
Adult↗
Ion-dependent generation of the electrochemical proton gradient delta muH+ in reconstituted plasma membrane vesicles from the yeast Metschnikowia reukaufii.
Plasma membrane vesicles were reconstituted by freezing and thawing of purified plasma membrane fraction from the yeast Metschnikowia reukaufii and phosphatidylcholine (type II-S from Sigma). The reconstituted plasma membrane vesicles generated a proton gradient (acidic inside) upon addition of ATP in presence of alkali cations. delta pH generation was most efficient when K+ was present both outside and inside the plasma membrane vesicles. Both ATPase activity and proton translocation in plasma membrane vesicles were inhibited by orthovanadate (50% inhibition at 100 microM). Plasma membrane vesicles reconstituted without added phosphatidylcholine generated in addition to delta pH, also an electrical potential difference delta psi (inside positive). Delta psi generation exhibited no K+ specificity. 50 microM dicyclohexylcarbodiimide inhibited completely delta psi generation whereas the K+-channel blocker quinine (5 microM) caused an 8-fold increase of delta psi. The proton gradient was much less affected by the agents. Taking into account the K+-dependent stimulation of the plasma membrane ATPase of M. reukaufii, these results further support the conclusion that the ATPase operates as a partially electrogenic H+/K+ exchanger, as was also suggested for other yeast plasma membrane ATPases.
Adenosine Triphosphatases↗