EVOLUTION OF REDOX REACTIVITY IN CYTOCHROME B

氧化还原电位决定了代谢过程中可能产生的能量，也是氧化还原反应进行速度的关键决定因素。了解控制氧化还原反应性的因素代表了电子转移蛋白结构-功能关系的当前前沿。血红素蛋白细胞色素bw2被用作研究氧化还原电位和氧化还原反应性在系统变体库中的共同进化的范例。功能通过血红素附近残基的单个或成对突变而进化。热力学势（EO）和氧化还原反应性（自交换率和交叉交换率）均被测量。每个位置上所有可能的变异（所有20个氨基酸）都被克隆出来，一个简单的彩色屏幕允许确定保留了b型血红素结构和亲和力的突变体。极值被用作下一代变体的祖先。比较这些突变体中氧化还原电位的变化与动力学反应性的变化（在马库斯理论的背景下）将使我们深入了解这两种特性之间的进化耦合程度。

The redox potential sets the energy yield possible in metabolism, and is also a key determinant of the rate at which the redox reaction proceeds. Understanding the factors that govern redox reactivity represents a current frontier in structure-function relationships for electron transfer proteins. The heme protein cytochrome bw2 is used as a paradigm to study the co-evolution of redox potential and redox reactivity within a systematic library of variants. Function evolves by single or pair wise mutations of residues in the vicinity of the heme. Both thermodynamic potential (EO) and redox reactivity (self exchange and cross exchange rates) are measured. All possible variants (all 20 amino acids) at each position are cloned, and a simple color screen allows the mutants that have retained both structure and affinity for the b-type heme to be determined. The extrema are used as progenitors of the next generation of variants. Comparing the variation of redox potential with that of the kinetic reactivity (within the context of Marcus theory) in these mutants will give insights into the degree of evolutionary coupling between these two properties.