Sakai H, Tsukihara T
Institute for Protein Research, Osaka University, Suita, Osaka, 565-0871, Japan.
J Biochem. 1998 Dec 1;124(6):1051-9. doi: 10.1093/oxfordjournals.jbchem.a022199.
Following determination of the first crystal structure of the reaction center of Rhodopseudomonas viridis, a membrane protein, by X-ray crystal structure analysis at 3.0 A resolution, 18 X-ray crystal structures and two electron crystal structures of membrane proteins have been obtained at higher than 3.5 A resolution. Besides these integral membrane protein structures, three crystal structures of water-soluble proteins, which can enter membranes, have been determined by X-ray crystallography at high resolution. The structural features of membrane proteins have been summarized by inspecting these crystal structures. The polypeptide chain crosses the membrane in a helical conformation or a beta-strand. The central +10 A region of the transmembrane alpha-helix is dominated by hydrophobic residues. On both sides of the central region are concentrated polar aromatic residues. Charged residues are dominant around +15 A to +20 A. All the transmembrane beta-structures are found in pore-forming proteins. The central region of the transmembrane beta-structure is amphipathic with hydrophobic residues on the membrane exposed side. The distribution of amino acid residues on the membrane exposed surface of the transmembrane beta-structure is similar to that of the transmembrane alpha-helix. alpha-Helices anchoring the membrane surface region are amphipathic with hydrophobic residues inside and hydrophilic residues outside.
通过3.0埃分辨率的X射线晶体结构分析确定了绿色红假单胞菌反应中心（一种膜蛋白）的首个晶体结构后，已获得了18个高于3.5埃分辨率的膜蛋白X射线晶体结构和两个电子晶体结构。除了这些完整的膜蛋白结构外，还通过高分辨率X射线晶体学确定了三种可进入膜内的水溶性蛋白的晶体结构。通过检查这些晶体结构总结了膜蛋白的结构特征。多肽链以螺旋构象或β链穿过膜。跨膜α螺旋的中心+10埃区域主要由疏水残基占据。在中心区域的两侧集中了极性芳香族残基。带电残基在+15埃至+20埃处占主导地位。所有跨膜β结构均存在于成孔蛋白中。跨膜β结构的中心区域具有两亲性，在膜暴露侧有疏水残基。跨膜β结构在膜暴露表面的氨基酸残基分布与跨膜α螺旋相似。锚定在膜表面区域的α螺旋具有两亲性，内部为疏水残基，外部为亲水残基。
