Hrabeta-Robinson E, Semadeni M, Packer L
Applied Science Division, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
Arch Biochem Biophys. 1989 Mar;269(2):476-84. doi: 10.1016/0003-9861(89)90131-8.
To investigate the site specificity of cation binding to bacteriorhodopsin, carboxyl groups were chemically modified in purple membrane preparations from Halobacterium halobium. Cation binding followed by EPR and visible spectroscopy has led us to the conclusion that two cations bind to the surface regions and that at least one cation binds to carboxyl groups in the protein interior. Conformational freedom is necessary for the cooperative conversion of deionized blue species to cation-reconstituted purple species. Studies of white membranes from the JW-5 strain showed that a higher content of charged lipids results in the binding of approximately 100 more color-regulating cations and in negative cooperativity in the blue-to-purple species conversion. A greater dependence of protein structure on these bound cations suggests a role for cations in the modulation of opsin-lipid interaction.
为了研究阳离子与细菌视紫红质结合的位点特异性，对嗜盐嗜盐菌紫色膜制剂中的羧基进行了化学修饰。通过电子顺磁共振（EPR）和可见光谱对阳离子结合进行的研究使我们得出以下结论：两个阳离子结合到表面区域，并且至少有一个阳离子结合到蛋白质内部的羧基上。去离子化蓝色物种向阳离子重构紫色物种的协同转化需要构象自由度。对JW - 5菌株白色膜的研究表明，较高含量的带电脂质会导致大约多100个颜色调节阳离子的结合，并在蓝色到紫色物种的转化中产生负协同效应。蛋白质结构对这些结合阳离子的更大依赖性表明阳离子在视蛋白 - 脂质相互作用的调节中起作用。
