Kinetics and pH-dependence of glycine-proton symport in Saccharomyces cerevisiae.
Kinetics and pH-dependence of glycine-proton symport in Saccharomyces cerevisiae.
复制标题
酿酒酵母中甘氨酸-质子共转运的动力学和 pH 依赖性。
DOI：
10.1016/0005-2736(84)90442-5
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Slayman,CL
中科院分区：
文献类型：
--
作者：
Ballarin-Denti,A;DenHollander,JA;Sanders,D;Slayman,CW;Slayman,CL
Interactions between intercellular pH (pH i) and H+-coupled transmembrane transport of glycine have been studied by means of 31 P-NMR, using both aerobic and ‘energy starved’cells of the yeast Saccharomyces cerevisiae. The general features of glycine transport in the yeast strain used (NCYC 239) are similar to those already reported for Saccharomyces carlsbergensis and S. cerevisiae, there being two kinetically distinct glycine uptake systems, with pH-independent K 1 2 values near 14 and 0.4 mM, respectively, but pH-dependent maximal velocities. Glycine transport itself has no measurable effect on pH i in aerobic cells, and only a marginal effect in energy-starved cells, but changes of pH i, imposed by extracellular addition of butyric acid, strongly influence glycine transport. Indeed, the dependence of glycine influx (in energy-starved cells) upon cytoplasmic H+ concentration appears to be third order, showing Hill slopes of 2.7–3.0. A crucial kinetic role for cytoplasmic pH in glycine transport is further indicated by a proportionality between the decline of flux and the decline of pH i produced by various metabolic inhibitors and uncouplers. Extracellular pH (pH o, by contrast, has only a weak effect on glycine influx, showing a Hill slope of 0.5. The major observations can be accommodated by a simple cyclic carrier scheme, in which 2 or more protons are transported along with glycine, but only one extracellular proton binding site dissociates in the testing range, with ap K near 5.5. The model requires a finite membrane potential, which must be somewhat sensitive to both pH i and pH o, and accomodates the discrepancy between measured net proton flux (one per glycine) and the kinetically required proton flux (two or more per glycine) by shunting through other proton-conducting pathways in the yeast membrane.
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影响因子：
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作者：
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DOI：
--
发表时间：
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期刊：
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影响因子：
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DOI：
10.1126/science.6867717
发表时间：
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期刊：
Science (New York, N.Y.)
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作者：
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