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首页> 外文期刊>Biochemistry >Nonequivalence of the nucleotide-binding subunits of an ABC transporter, the histidine permease, and conformational changes in the membrane complex.
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Nonequivalence of the nucleotide-binding subunits of an ABC transporter, the histidine permease, and conformational changes in the membrane complex.

机译：ABC转运蛋白的核苷酸结合亚基，组氨酸通透酶和膜复合物中的构象变化无与伦比。

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摘要

The membrane-bound complex of the Salmonella typhimurium histidine permease, an ABC transporter (or traffic ATPase), is composed of two membrane proteins, HisQ and HisM, and two identical copies of an ATP-hydrolyzing protein, HisP. We have developed a technique that monitors quantitatively the sulfhydryl modification levels within the intact complex, and we have used it to investigate whether the HisP subunits behave identically within the complex. We show here that they interact differently with various thiol-specific reagents, thus indicating that, despite being identical, they are arranged asymmetrically. The possible basis of this asymmetry is discussed. We have also analyzed the occurrence of conformational changes during various stages of the activity cycle using thiol-specific reagents, fluorescence measurements, and circular dichroism spectroscopy. Cys-51, located close to the ATP-binding pocket, reflects conformational changes upon binding of ATP but does not participate in changes involved in signaling and translocation. The latter are shown to cause secondary structure alterations, as indicated by changes in alpha-helices; tertiary structure alterations also occur, as shown by fluorescence studies.
机译：鼠伤寒沙门氏菌组氨酸通透酶的膜结合复合物，一种ABC转运蛋白（或运输ATPase），由两个膜蛋白HisQ和HisM以及两个相同拷贝的ATP水解蛋白HisP组成。我们已经开发出一种技术，可以定量监测完整复合物中的巯基修饰水平，并且我们已经使用它来研究HisP亚基在复合物中的行为是否相同。我们在这里表明它们与各种硫醇特异性试剂的相互作用不同，因此表明尽管它们相同，但它们是不对称排列的。讨论了这种不对称的可能基础。我们还使用硫醇特异性试剂，荧光测量和圆二色光谱分析了活动周期各个阶段构象变化的发生。位于靠近ATP结合袋的Cys-51反映了ATP结合后的构象变化，但不参与信号转位中的变化。如α-螺旋的变化所表明的，后者显示出引起二级结构改变。如荧光研究所示，三级结构也发生改变。

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