LIGHT DRIVEN ION TRANSPORT IN BACTERIAL RHODOPSINS

在目前讨论的用于许多离子泵的机制中， 单个结合位点在两个膜表面之间交替， 依赖于产生能量的反应，而传输的离子是 通过特定的途径在这个地方来回传播光驱动 质子和氯离子泵，细菌视紫红质和盐视紫红质， 理想的系统来研究这种全球性和局部性的 过程相互作用，以确保离子的单向运动， 膜。虽然它的细节是特定于两种细菌 视紫红质，交替访问机制确定的原则， 可适用于其他离子泵：a）通过小的局部接入控制 活性位点的结构变化，B）控制两种替代方案 通过局部静电效应的整体蛋白质构象，c） 通过改变结合亲和力和内部离子转移 蛋白质结构域中的介电环境，d）特异性的控制 通过微妙。运输离子的氢键的差异， 它的结合位点，和e）的偶极子性质的基本参与， 结合水在离子迁移的所有过程中。研究 该建议中的策略是基于质子的相似性， 氯离子泵到另一个，最近发现，一个单一的氨基， 酸置换将一种的特异性改变为另一种。 这种重组视网膜蛋白将随着时间的推移而被检验- 可见光和红外线的分辨光谱学， 晶体学和自旋标记探针的性质a）通过e）在 为了区分与绑定相关的结构和过程， 从参与进入的那些离子中传输的离子的传导 结合位点的变化。

In the currently discussed mechanism for many ion pumps, the access of a single binding site alternates between the two membrane surfaces, dependent on an energy-yielding reaction, while the transported ion is conducted to and from this site by specific pathways. The light-driven proton and chloride ion pumps, bacteriorhodopsin and halorhodopsin, are ideal systems to study the mechanism in which such global and local processes interact to ensure the unidirectional movement of the ion across the membrane. Although its details are specific to the two bacterial rhodopsins, the alternating access mechanism identifies principles that may apply to other ion pumps: a) control of local access through small structural changes at the active site, b) control of two alternative global protein conformations through local electrostatic effects, c) control of binding affinity and internal ion transfer through changing dielectric environments in proteins domains, d) control of specificity through subtle. differences in hydrogen bonding of the transported ion at its binding site, and e) essential involvement of the dipole properties of bound water in all processes of the ion translocation. The research strategy in this proposal is based on the similarity of the proton and chloride pumps to one another, and the recent finding that a single amino acid replacement changed the specificity of one into the other. Recombinant retinal proteins of this kind will be examined with time- resolved spectroscopy in the visible and the infrared, x-ray crystallography, and spin-label probes for properties a) through e) in order to distinguish structures and processes relevant to the binding and conduction of the transported ions from those involved in the access change of the binding sites.