Proton transfer pathways in bacteriorhodopsin at 2.3 Angstrom resolution
Proton transfer pathways in bacteriorhodopsin at 2.3 Angstrom resolution
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DOI：
10.1126/science.280.5371.1934
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发表时间：
1998-06-19
期刊：
影响因子：
56.9
通讯作者：
Lanyi, JK
中科院分区：
文献类型：
--
作者：
Luecke, H;Richter, HT;Lanyi, JK
细菌视紫红质的视黄醛的光异构化引发了一个质子跨膜易位的循环反应。对这种蛋白质的研究有望更好地了解离子泵的功能。结合大量的光谱和突变数据，细菌视紫红质的原子结构，在过去十年中以越来越高的分辨率确定，提出了看似合理但往往相互矛盾的机制。在立方脂相中生长的细菌视紫红质晶体的X射线衍射揭示了意想不到的双重对称性，这表明沿着晶体学c轴沿着的半面体孪生。考虑到这种孪晶，结构精确到2.3埃，与早期的模型不同，包括最近报道的模型。质子受体Asp（85）的一个羧基氧原子通过氢键合的水连接到质子供体，即网膜席夫碱，并与另一个水形成第二个氢键。Asp（85）的另一个羧基氧原子接受来自Thr（89）的氢键。这种结构形成活性位点。附近的Arg（82）是许多氢键残基和有序水分子网络的中心。该网络定义了质子从埋藏的席夫碱到细胞外表面的途径。
Photoisomerization of the retinal of bacteriorhodopsin initiates a cyclic reaction in which a proton is translocated across the membrane. Studies of this protein promise a better understanding of how ion pumps function. Together with a large amount of spectroscopic and mutational data, the atomic structure of bacteriorhodopsin, determined in the last decade at increasing resolutions, has suggested plausible but often contradictory mechanisms. X-ray diffraction of bacteriorhodopsin crystals grown in cubic lipid phase revealed unexpected two-fold symmetries that indicate merohedral twinning along the crystallographic c axis. The structure, refined to 2.3 angstroms taking this twinning into account, is different from earlier models, including that most recently reported. One of the carboxyl oxygen atoms of the proton acceptor Asp(85) is connected to the proton donor, the retinal Schiff base, through a hydrogen-bonded water and forms a second hydrogen bond with another water. The other carboxyl oxygen atom of Asp(85) accepts a hydrogen bond from Thr(89). This structure forms the active site. The nearby Arg(82) is the center of a network of numerous hydrogen-bonded residues and an ordered water molecule. This network defines the pathway of the proton from the buried Schiff base to the extracellular surface.