X-ray structure determination of the cytochrome c2:: Reaction center electron transfer complex from Rhodobacter sphaeroides
X-ray structure determination of the cytochrome c2:: Reaction center electron transfer complex from Rhodobacter sphaeroides
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DOI：
10.1016/s0022-2836(02)00168-7
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发表时间：
2002-05-31
影响因子：
5.6
通讯作者：
Feher, G
中科院分区：
文献类型：
--
作者：
Axelrod, HL;Abresch, EC;Feher, G
在光合细菌球形红细菌中，水溶性细胞色素c（2）（cyt c（2））是反应中心（RC）的电子供体，RC是膜结合的色素-蛋白质复合物，是主要光诱导电子转移的位点。为了确定在两种蛋白质的瞬时结合复合物中对接和电子转移的重要相互作用，RC和cyt c（2）以两种单斜晶体形式共结晶。Cyt c（2）在大约0.9 μ s的时间内还原共晶体中光氧化的RC供体（D+），一种细菌叶绿素二聚体，这与在溶液中测量的时间相同。这提供了强有力的证据表明，在电子转移区域的复合物的结构是相同的晶体和溶液中。x射线衍射从共晶收集数据，最大分辨率为2.40埃，并精确到R因子为22%（无R = 26%）。该结构显示cyt c（2）位于RC周质表面的中心，血红素边缘位于细菌叶绿素二聚体上方。两个辅因子的最近原子之间的距离是8.4埃。Tyr L162的侧链使货车德瓦尔斯与两个辅因子沿着最短的分子间电子转移途径接触。结合界面可以分为两个结构域：（i）短程相互作用结构域，其包括Tyr L162和表现出非极性相互作用、氢键和阳离子-π相互作用的基团。该结构域有助于cyt c（2）结合的强度和特异性。(ii)一种长程静电相互作用结构域，在RC和cyt c上含有溶剂化互补电荷（2）。这个结构域除了有助于结合之外，还可以帮助引导未结合的蛋白质朝向正确的构象。(C)2002爱思唯尔科技有限公司版权所有。
In the photosynthetic bacterium Rhodobacter sphaeroides, a water soluble cytochrome c(2) (cyt c(2)) is the electron donor to the reaction center (RC), the membrane-bound pigment-protein complex that is the site of the primary light-induced electron transfer. To determine the interactions important for docking and electron transfer within the transiently bound complex of the two proteins, RC and cyt c(2) were co-crystallized in two monoclinic crystal forms. Cyt c(2) reduces the photo-oxidized RC donor (D+), a bacteriochlorophyll dimer, in the co-crystals in similar to0.9 mus, which is the same time as measured in solution. This provides strong evidence that the structure of the complex in the region of electron transfer is the same in the crystal and in solution. X-ray diffraction. data were collected from co-crystals to a maximum resolution of 2.40 Angstrom and refined to an R-factor of 22% (R-free = 26%). The structure shows the cyt c(2) to be positioned at the center of the periplasmic surface of the RC, with the heme edge located above the bacteriochlorophyll dimer. The distance between the closest atoms of the two cofactors is 8.4 Angstrom. The side-chain of Tyr L162 makes van der Waals contacts with both cofactors along the shortest intermolecular electron transfer pathway. The binding interface can be divided into two domains: (i) A short-range interaction domain that includes Tyr L162, and groups exhibiting non-polar interactions, hydrogen bonding, and a cation-pi interaction. This domain contributes to the strength and specificity of cyt c(2) binding. (ii) A long-range, electrostatic interaction domain that contains solvated complementary charges on the RC and cyt c(2). This domain, in addition to contributing to the binding, may help steer the unbound proteins toward the right conformation. (C) 2002 Elsevier Science Ltd. All rights reserved.