THE ARGININE RESIDUE IN THE PROTON MOTIVE PHOTO CYCLE OF BACTERIORHODOPSIN

细菌视紫红质结构，由电子推导而来 紫膜中二维晶体的显微数据 最新的数据来自于在脂质中生长的微晶体的X射线数据 立方相，表明在蛋白质的静止状态下，大多数 可电离残基(天冬氨酸、谷氨酸、精氨酸和赖氨酸)非常接近或接近 两种膜表面，除天冬氨酸-L 15，天冬氨酸-2 12， ASP-85和Arg-82。最后三个残留物，连同一个或多个 水分子，形成质子化希夫的络合反离子 以(某人)为基地[N1]质子动光循环的CP/MAS研究 Arg-BR在0.1M的氯化钠，pH=10的条件下，鉴定出精氨酸残基 其环境在bR568和br568之间的过渡过程中发生变化 早期的M州。这种变化在后期的M状态中持续存在，并且 通过两个翼峰的出现而显现出来，被24个分开 Ppm，在其他六种精氨酸的中心共振的侧翼 侧链。精氨酸III高度不对称的相同信号 环境在黄色M-like(0.3M Gdn.HCJ， PH=0.8)和类蓝色0(0.1M氯化钠，pH=6.5)暗适应型 D85N突变体。野生型M状态之间的相似性 和D85N碱性形式，它们起源于 残留物85的Sb和中性表明 从附近的R82行驶。更多的证据来自延迟的 CP实验，它从交叉极化的核中分离出信号 水可交换的质子。翼状山峰不见了 类M的D85N的延迟CP谱，这表明它们确实存在 不属于表面残留物。此作业与以下内容一致 R82参与bR568的席夫碱反离子络合物 (连同D85和D212)，并将R82重新定向到 处于M状态的蛋白质的胞外(EC)侧。这 解释也与R82突变对 光循环动力学和R82控制pKA的概念 D85的S和欧共体质子释放组。自.以来 Sb的质子化状态似乎并不影响 D85N(Sb在pH=6.5时质子化，在pH=10.8时去质子化)， 胍基含氮化合物化学环境的研究 处于N状态的野生型光循环正在进行中。

The bacteriorhodopsin structure, deduced from the electron microscopy data of two-din~ensional crystals in the purple membrane and most recently from X-ray data of microcrystals grown in lipidic cubic phases, shows that in the resting state of the protein, most of the ionizable residues (Asp, Glu, Arg and Lys) are very close to or at the two membrane surfaces, with the exception of Asp-l 15, Asp-2 12, Asp-85 and Arg-82. The last three residues, together with one or more water molecules, form the complex counterion of the protonated Schiff base (SB). CP/MAS studies of the proton-motive photo-cycle of [N1 2-5N2]Arg-bR in 0.1 M NaCl, pH=lO have identified an arginine residue whose environment changes in the transition between the bR568 and the early M states. This change persists in the late M state, and manifests itself by the appearance of two 'wing peaks, separated by 24 ppm, that flank the central resonance of the other six arginine sidechains. The same signal for an arginine iii a highly asymmetric environment is reproduced in the yellow M-like (0.3 M Gdn.HCJ, pH=l0.8) and the blue 0-like (0.1 M NaCl, pH=6.5) dark-adapted forms of the D85N mutant. The similarities between the wild type M state and the D85N alkaline form, which originate from the deprotonation of the SB and the neutrality of residue 85, suggest that the 'wing peaks arise from the nearby R82. Additional evidence comes from the delayed CP experiment, which isolates signals from nuclei cross polarized from water exchangeable protons. The 'wingt peaks are missing from the delayed CP spectrum of the M-like D85N, which indicates that they do not belong to a surface residue. This assignment is consistent with participation of R82 in the Schiff base counterion complex in bR568 (together with D85 and D2 12), and reorientation of R82 towards the extracellular (EC) side of the protein in the M state. This interpretation is also consistent with the effects of R82 mutations on the photo-cycle kinetics and with the notion that R82 controls the pKa s of D85 and the proton release group at the EC. Since the protonation state of the SB does not seem to affect the 'wing peaks in D85N (the SB is protonated at pH=6.5 and deprotonated at pH=lO.8), studies to clarify the chemical environment of the guanidyl nitrogens in the N state of the wild type photo-cycle are under way.