Luecke H, Schobert B, Richter H T, Cartailler J P, Lanyi J K
Department of Molecular Biology and Biochemistry, University of California, Irvine, CA, 92697, USA.
J Mol Biol. 1999 Aug 27;291(4):899-911. doi: 10.1006/jmbi.1999.3027.
Th?e atomic structure of the light-driven ion pump bacteriorhodopsin and the surrounding lipid matrix was determined by X-ray diffraction of crystals grown in cubic lipid phase. In the extracellular region, an extensive three-dimensional hydrogen-bonded network of protein residues and seven water molecules leads from the buried retinal Schiff base and the proton acceptor Asp85 to the membrane surface. Near Lys216 where the retinal binds, transmembrane helix G contains a pi-bulge that causes a non-proline? kink. The bulge is stabilized by hydrogen-bonding of the main-chain carbonyl groups of Ala215 and Lys216 with two buried water molecules located between the Schiff base and the proton donor Asp96 in the cytoplasmic region. The results indicate extensive involvement of bound water molecules in both the structure and the function of this seven-helical membrane protein. A bilayer of 18 tightly bound lipid chains forms an annulus around the protein in the crystal. Contacts between the trimers in the membrane plane are mediated almost exclusively by lipids.
通过对立方脂质相中生长的晶体进行X射线衍射，确定了光驱动离子泵细菌视紫红质及其周围脂质基质的原子结构。在细胞外区域，蛋白质残基和七个水分子形成的广泛三维氢键网络从埋藏的视黄醛席夫碱和质子受体Asp85延伸至膜表面。在视黄醛结合的Lys216附近，跨膜螺旋G含有一个导致非脯氨酸扭结的π-凸起。该凸起通过Ala215和Lys216的主链羰基与位于细胞质区域席夫碱和质子供体Asp96之间的两个埋藏水分子形成氢键而得以稳定。结果表明，结合水分子广泛参与了这种七螺旋膜蛋白的结构和功能。晶体中，由18条紧密结合的脂质链形成的双层围绕蛋白质形成一个环。膜平面中三聚体之间的接触几乎完全由脂质介导。
