Functional significance of a protein conformation change at the cytoplasmic end of helix F during the bacteriorhodopsin photocycle.
Functional significance of a protein conformation change at the cytoplasmic end of helix F during the bacteriorhodopsin photocycle.
复制标题
细菌视紫红质光循环过程中螺旋 F 细胞质末端蛋白质构象变化的功能意义。
DOI：
10.1016/s0006-3495(95)80081-0
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Lanyi,JK
中科院分区：
文献类型：
--
作者：
Brown,LS;Varo,G;Needleman,R;Lanyi,JK
光驱动质子泵细菌视紫红质光周期的后半部分包括 D96 和视网膜希夫碱之间（M 到 N 反应）以及细胞质表面和 D96 之间（N 中间体的衰变）之间的质子转移。水活性降低和静水压增加的抑制作用表明，质子从 D96 转移到席夫碱需要构象变化，从而导致细胞质区域更大的水合作用，并且提出了以下可能性：D96 随后从细胞质表面重新质子化可能需要逆转这一过程。 M 中间体的电子衍射表明螺旋 F 的细胞质末端倾斜。将大基团（例如各种马来酰亚胺标记）引入到螺旋 A、B、C、E 和 G 的细胞质末端的工程化半胱氨酸中，仅对 M 和 N 的衰变产生较小的扰动，但当标记与螺旋 F 连接时，这些反应会发生重大变化。在这些样品中，席夫碱的重质子化被加速，而 D96 的重质子化被强烈延迟。在这个位置而不是在其他位置引入二苯甲酮的交联会引起相反的变化：席夫碱的重质子化大大减慢，而 D96 的重质子化则加速。我们得出的结论是，与衍射结构一致，光周期后半部分的质子转移是通过螺旋 F 的细胞质末端的运动促进的，首先远离蛋白质中心，然后返回。
The second half of the photocycle of the light-driven proton pump bacteriorhodopsin includes proton transfers between D96 and the retinal Schiff base (the M to N reaction) and between the cytoplasmic surface and D96 (decay of the N intermediate). The inhibitory effects of decreased water activity and increased hydrostatic pressure have suggested that a conformational change resulting in greater hydration of the cytoplasmic region is required for proton transfer from D96 to the Schiff base, and have raised the possibility that the reversal of this process might be required for the subsequent reprotonation of D96 from the cytoplasmic surface. Tilt of the cytoplasmic end of helix F has been suggested by electron diffraction of the M intermediate. Introduction of bulky groups, such as various maleimide labels, to engineered cysteines at the cytoplasmic ends of helices A, B, C, E, and G produce only minor perturbation of the decays of M and N, but major changes in these reactions when the label is linked to helix F. In these samples the reprotonation of the Schiff base is accelerated and the reprotonation of D96 is strongly retarded. Cross-linking with benzophenone introduced at this location, but not at the others, causes the opposite change: the reprotonation of the Schiff base is greatly slowed while the reprotonation of D96 is accelerated. We conclude that, consistent with the structure from diffraction, the proton transfers in the second half of the photocycle are facilitated by motion of the cytoplasmic end of helix F, first away from the center of the protein and then back.