Crystallographic structures of the M and N intermediates of bacteriorhodopsin: assembly of a hydrogen-bonded chain of water molecules between Asp-96 and the retinal Schiff base.
Crystallographic structures of the M and N intermediates of bacteriorhodopsin: assembly of a hydrogen-bonded chain of water molecules between Asp-96 and the retinal Schiff base.
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细菌视紫红质 M 和 N 中间体的晶体结构：Asp-96 和视网膜席夫碱之间水分子氢键链的组装。
DOI：
10.1016/s0022-2836(03)00576-x
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发表时间：
2003
影响因子：
5.6
通讯作者：
Lanyi,JanosK
中科院分区：
文献类型：
--
作者：
Schobert,Brigitte;Brown,LeonidS;Lanyi,JanosK
野生型细菌视紫红质的 M 中间体和 V49A 突变体的 N 中间体在 pH 5.6 和 295 K 的光稳态下积累，并且它们的晶体结构分别确定为 1.52Å 和 1.62Å 分辨率。它们在序列中似乎是M1和N'，M1↔M2↔M'2↔N↔N'→O→BR，其中M1、M2和M'2在重定向转换之前和之后以及质子释放到细胞外表面之后包含未质子化的视网膜希夫碱，而N和N’在Asp96从细胞质重新质子化之前和之后包含重新质子化的希夫碱表面。在 M1 中，我们在 Asp96 处检测到三个氢键水分子簇，这在 BR 状态中不存在。在我们之前报道过的 M2 结构中，其中一个水分子插入到 Asp96 和 Thr46 之间。在 N' 中，簇转变为由四个水分子组成的单列氢键链，将 Asp96 连接到希夫碱。我们在未照射的 F219L 突变体晶体结构中的残基 219 附近发现了三个水分子的网络，其中残基替换形成了一个空腔。这表明我们在 N' 中观察到的细胞质区域的水合作用可能是自发发生的，从作为核的现有水分子开始，在光循环中残基重排的空腔中。
An M intermediate of wild-type bacteriorhodopsin and an N intermediate of the V49A mutant were accumulated in photostationary states at pH 5.6 and 295 K, and their crystal structures determined to 1.52Å and 1.62Å resolution, respectively. They appear to be M1and N′ in the sequence, M1↔M2↔M′2↔N↔N′→O→BR, where M1, M2, and M′2contain an unprotonated retinal Schiff base before and after a reorientation switch and after proton release to the extracellular surface, while N and N′ contain a reprotonated Schiff base, before and after reprotonation of Asp96 from the cytoplasmic surface. In M1, we detect a cluster of three hydrogen-bonded water molecules at Asp96, not present in the BR state. In M2, whose structure we reported earlier, one of these water molecules intercalates between Asp96 and Thr46. In N′, the cluster is transformed into a single-file hydrogen-bonded chain of four water molecules that connects Asp96 to the Schiff base. We find a network of three water molecules near residue 219 in the crystal structure of the non-illuminated F219L mutant, where the residue replacement creates a cavity. This suggests that the hydration of the cytoplasmic region we observe in N′ might have occurred spontaneously, beginning at an existing water molecule as nucleus, in the cavities from residue rearrangements in the photocycle.