Kinetics of reduction of high redox potential ferredoxins by the semiquinones of Clostridium pasteurianum flavodoxin and exogenous flavin mononucleotide. Electrostatic and redox potential effects.
Kinetics of reduction of high redox potential ferredoxins by the semiquinones of Clostridium pasteurianum flavodoxin and exogenous flavin mononucleotide. Electrostatic and redox potential effects.
复制标题
巴氏梭菌黄素氧还蛋白半醌和外源黄素单核苷酸还原高氧化还原电位铁氧还蛋白的动力学。
DOI：
10.1021/bi00341a054
复制
发表时间：
1985
期刊：
影响因子：
2.9
通讯作者：
Cusanovich,MA
中科院分区：
文献类型：
--
作者：
Przysiecki,CT;Cheddar,G;Meyer,TE;Tollin,G;Cusanovich,MA
C. T. Przysiecki， G. Cheddar， T. E. Meyer， G. Tollin, and。摘要：研究了10种高氧化还原电位铁氧还蛋白（hiip’s）与黄酮单核苷酸（FMN）和黄氧还蛋白半醌类电子转移反应速率常数的离子强度依赖性。速率常数被外推到无限离子强度通过使用静电相互作用的理论模型在我们的实验室开发。在所有情况下，静电相互作用的符号与蛋白质净电荷相同，但大小要小得多。结果与电荷近似均匀分布在hiip表面的模型一致，其中存在短期和长期静电相互作用。vinosum Chromatium hiip的静电场计算与此一致。假定的电子转移位置包括蛋白质表面的铁硫簇最接近的区域，并且看起来相对疏水。主要的短程静电相互作用涉及铁硫簇上的负电荷。对于一些净带负电荷的蛋白质，这种效应被放大，而对于净带正电荷的hiip，这种效应被抵消。外推到无限离子强度的速率常数可以与反应物之间的氧化还原电位差相关，正如先前在细胞色素-黄素半醌反应中所显示的那样。与FMN半醌- hiip反应相比，黄伏还毒素半醌的静电和氧化还原电位效应都被放大。这在之前的黄素半醌-细胞色素反应中也被观察到。目前的工作进一步支持了这些因素（氧化还原电位差和空间和静电相互作用）的普遍性，我们发现这些因素控制着氧化还原蛋白电子转移反应的速率，因此决定了生物特异性。
C. T. Przysiecki, G. Cheddar, T. E. Meyer, G. Tollin, and. A. Cusanovich* Department of Biochemistry, University of Arizona, Tucson, Arizona 85721 Received February 25, 1985 abstract: We have measured the ionic strength dependence of the rate constants for the electron-transfer reactions of flavinmononucleotide (FMN) and flavodoxin semiquinones with 10 high redox potential ferredoxins (HiPIP’s). The rate constants were extrapolated to infinite ionic strength by using a theoretical model of electrostatic interactions developed in our laboratory. In all cases, the sign of the electrostatic interaction was the same as the protein net charge, but the magnitudes were much smaller. The results are consistent with a model in which the electrical charges are approximately uniformly distributed over the HiPIP surface and in which there are both short-and long-range electrostatic interactions. An electrostatic field calculation for Chromatium vinosum HiPIP is consistent with this. The presumed site of electron transfer includes that region of the protein surfaceto which the iron-sulfur cluster is nearest and appears to be relatively hydrophobic. The principal short-range electrostatic interaction would involve the negative charge on the iron-sulfur cluster. For some net negatively charged proteins, this effect is magnified, and for net positively charged HiPIP’s, it is counterbalanced. The rate constants extrapolated to infinite ionic strength can be correlated with redox potential differences between the reactants, as has previously been shown for cytochrome-flavin semiquinone reactions. Both electrostatic and redox potential effects are magnified for the flavodoxin semiquinone as compared to the FMN semiquinone-HiPIP reactions. This was also observedpreviously for the flavin semiquinone-cytochrome reactions. The present work provides further support for the universal nature of those factors (redox potential differences and steric and electrostatic interactions) which we have found to govern the rates of redox protein electron-transfer reactions and which therefore determine biological specificity.