Interactions between lipids and bacterial reaction centers determined by protein crystallography
Interactions between lipids and bacterial reaction centers determined by protein crystallography
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DOI：
10.1073/pnas.162368399
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发表时间：
2002-08-20
影响因子：
11.1
通讯作者：
Allen, JP
中科院分区：
文献类型：
--
作者：
Camara-Artigas, A;Brune, D;Allen, JP
利用x射线衍射在2.55埃的分辨率下对球形红杆菌的反应中心结构进行了解析。位于蛋白质表面的三个脂质分子在电子密度图中被分解。除了先前报道的一种心磷脂外[McAuley， k.e., Fyfe, p.k., Ridge, j.p., Isaacs, n.w., Cogdell, r.j.和Jones， m.r. (1999) Proc. Nad。国家科学。[USA 96,14706-14711]，细胞膜的另外两种主要脂质被发现，一种是磷脂酰胆碱，一种是葡萄糖半乳糖二酰基甘油。这三种脂质的存在已被激光质谱法证实。脂质位于蛋白质表面的疏水区域，主要与疏水氨基酸相互作用，特别是芳香残基。虽然心磷脂距离辅助因子超过15埃，但其他两种脂质与辅助因子密切接触，并可能导致两个辅助因子分支的能量学差异，这是导致电子转移不对称的主要原因。糖脂与活性细菌叶绿素单体的距离为3.5埃，并保护该辅助因子免受溶剂的影响，而非活性细菌叶绿素单体则明显暴露在更大的表面。磷脂酰胆碱的磷酸原子距离失活的菌藻素6.5埃，相关的静电相互作用可能有助于涉及该辅助因子的电子转移速率。总的来说，脂质跨越了大约30埃的距离，这与双层状排列一致，表明在膜蛋白周围存在脂质“内壳”，这对膜功能至关重要。
The structure of the reaction center from Rhodobacter sphaeroides has been solved by using x-ray diffraction at a 2.55-Angstrom resolution limit. Three lipid molecules that lie on the surface of the protein are resolved in the electron density maps. In addition to a cardiolipin that has previously been reported [McAuley, K. E., Fyfe, P. K., Ridge, J. P., Isaacs, N. W., Cogdell, R. J. & Jones, M. R. (1999) Proc. Nad. Acad Sci. USA 96,14706-14711], two other major lipids of the cell membrane are found, a phosphaticlylcholine and a glucosylgalactosyl diacylglycerol. The presence of these three lipids has been confirmed by laser mass spectroscopy. The lipids are located in the hydrophobic region of the protein surface and interact predominately with hydrophobic amino acids, in particular aromatic residues. Although the cardiolipin is over 15 Angstrom from the cofactors, the other two lipids are in close contact with the cofactors and may contribute to the difference in energetics for the two branches of cofactors that is primarily responsible for the asymmetry of electron transfer. The glycolipid is 3.5 Angstrom from the active bacteriochlorophyll monomer and shields this cofactor from the solvent in contrast to a much greater exposed surface evident for the inactive bacteriochlorophyll monomer. The phosphate atom of phosphatidylcholine is 6.5 Angstrom from the inactive bacteriopheophytin, and the associated electrostatic interactions may contribute to electron transfer rates involving this cofactor. Overall, the lipids span a distance of approximate to30 Angstrom, which is consistent with a bilayer-like arrangement suggesting the presence of an "inner shell" of lipids around membrane proteins that is critical for membrane function.