Electron transfer from cytochrome c(2) to the reaction center: a transition state model for ionic strength effects due to neutral mutations.
Electron transfer from cytochrome c(2) to the reaction center: a transition state model for ionic strength effects due to neutral mutations.
复制标题
DOI：
10.1021/bi901332t
复制
发表时间：
2009-12-08
期刊：
影响因子：
2.9
通讯作者：
Okamura, Melvin Y.
中科院分区：
文献类型：
--
作者：
Abresch, Edward C.;Gong, Xiao-Min;Paddock, Mark L.;Okamura, Melvin Y.
蛋白质间电子转移在生物能量转换中发挥着重要作用。在这项工作中，研究了细胞色素c2 (cyt) 和反应中心(RC) 之间的电子转移反应，以确定耦合缔合和电子转移的机制。先前的研究表明，反应界面中疏水残基的突变，特别是 Tyr L162，会改变低离子强度下的结合亲和力和电子转移速率。在本研究中，检查了离子强度对 cyt c2 与天然或突变 RC 之间的二级电子转移速率常数 k2 的影响。随着离子强度的增加，疏水性和氢键残基的突变导致 k2 降低得更快。这种变化用过渡态模型来解释，即从天然 RC 中的扩散限制反应（电子转移发生在每次结合事件时）转变为 Tyr L162 突变体中的快速交换反应（其中解离发生在电子转移之前，k2 取决于结合蛋白复合物和游离蛋白复合物之间的平衡）。离子强度依赖性的差异归因于与束缚态相比，离子强度对过渡态能量的影响较小，这是由于过渡态带电残基之间的距离较大。该模型解释了在较高离子强度下更快的解离速率，这可能有助于对生物功能重要的快速周转。这些结果为耦合蛋白质关联与电子转移提供了定量模型，并阐明了短程相互作用在确定电子转移速率中的作用。
Interprotein electron transfer plays an important role in biological energy conversion. In this work the electron transfer reaction between cytochrome c2 (cyt) and reaction center (RC) was studied to determine the mechanisms coupling association and electron transfer. Previous studies have shown that mutation of hydrophobic residues in the reaction interface, particularly Tyr L162, change the binding affinity and rates of electron transfer at low ionic strength. In this study the effect of ionic strength on the second order electron transfer rate constant k2, between cyt c2 and native or mutant RCs was examined. Mutations of hydrophobic and hydrogen bonding residues caused k2 to decrease more rapidly with increasing ionic strength. This change is explained with a transition state model by a switch from a diffusion-limited reaction in native RCs, where electron transfer occurs upon each binding event, to a fast exchange reaction in the Tyr L162 mutant, where dissociation occurs before electron transfer and k2 depends upon the equilibrium between bound and free protein complexes. The difference in ionic strength dependence is attributed to a smaller effect of ionic strength on the energy of the transition state compared to the bound state due to larger distances between charged residues in the transition state. This model explains the faster dissociation rate at higher ionic strength that may assist rapid turnover important for biological function. These results provide a quantitative model for coupling protein association with electron transfer and elucidate the role of short-range interactions in determining the rate of electron transfer.
登录
查看更多内容
DOI：
10.1073/pnas.89.8.3338
发表时间：
1992-04-15
影响因子：
11.1
作者：
NORTHRUP, SH;ERICKSON, HP
通讯作者：
ERICKSON, HP
影响因子：
2.3
作者：
AQUINO, AJA;BEROZA, P;ONUCHIC, JN
通讯作者：
ONUCHIC, JN
影响因子：
2.9
作者：
Crowley, PB;Carrondo, MA
通讯作者：
Carrondo, MA
影响因子：
5.6
作者：
Axelrod, HL;Abresch, EC;Feher, G
通讯作者：
Feher, G
影响因子：
2.9
作者：
Gerencsér, L;Laczkó, G;Maróti, P
通讯作者：
Maróti, P