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首页> 外文期刊>Biochemistry >LIGHT-DRIVEN CHLORIDE ION TRANSPORT BY HALORHODOPSIN FROM NATRONOBACTERIUM PHARAONIS .2. CHLORIDE RELEASE AND UPTAKE, PROTEIN CONFORMATION CHANGE, AND THERMODYNAMICS
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LIGHT-DRIVEN CHLORIDE ION TRANSPORT BY HALORHODOPSIN FROM NATRONOBACTERIUM PHARAONIS .2. CHLORIDE RELEASE AND UPTAKE, PROTEIN CONFORMATION CHANGE, AND THERMODYNAMICS

机译：盐细菌从藻类细菌中提取光驱动的氯离子迁移; 2。氯化物释放和摄取，蛋白质构象变化和热力学

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The photocycle of the light-driven chloride pump, N. pharaonis halorhodopsin, is described hv by the scheme HR -->/hv K --> double left right arrow L double left right arrow N double left right arrow O double left right arrow HR' --> HR. From the chloride dependencies of the rate constants in this model we identify the N --> O and O --> HR' reactions as the steps where chloride release and uptake occur, respectively, during the transport. The dependencies of the rate constants on temperature describe a thermodynamic cycle in which enthalpy-entropy conversion occurs in the O --> HR' reaction. The dependencies of the rate constants on hydrostatic pressure indicate that a substantial volume decrease occurs at the L --> N reaction, a result of a large-scale conformational change. This is the opposite of the volume increase in the photocycle of the proton pump, bacteriorhodopsin, that is implicated in the access change of-the active site during the transport and the passage of a proton from the cytoplasmic surface to the active site. The results together suggest a chloride transport mechanism, in which the equivalents of all the ion transfer steps in bacteriorhodopsin occur but in the reverse sense, so as to cause the extracellular-to-cytoplasmic translocation of a chloride ion instead of the cytoplasmic-to-extracellular transport of a proton. [References: 55]
机译：用方案HR-> / hv K->双左右箭头L双左右箭头N双左右箭头O双左右箭头来描述光驱动氯化物泵N. pharaonis halhohodopsin的光循环HR'-> HR。根据该模型中速率常数的氯化物依赖性，我们确定N-> O和O-> HR'反应为运输过程中分别发生氯释放和吸收的步骤。速率常数对温度的依赖性描述了一个热力学循环，在该循环中，在O-> HR'反应中发生了焓-熵转化。速率常数对静水压力的依赖性表明，在L-> N反应中，体积发生了大幅下降，这是大规模构象变化的结果。这与质子泵细菌视紫红质的光循环的体积增加相反，其与在质子从细胞质表面到活性位点的运输和通过期间活性位点的进入改变有关。这些结果共同表明了氯离子的转运机理，其中细菌视紫红质中所有离子转移步骤均发生，但反过来，从而导致氯离子从细胞外到细胞质的转运，而不是从细胞质到细胞质的转运。质子的细胞外运输。 [参考：55]

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