The pH dependence of intramolecular electron transfer in azurins

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• 作者：Farver ; Ole ; Bonander ; Nicklas ; Skov ; Lars K. ; Pecht ; Israel
• 关键词：Copper protein ; Mutagenesis ; Pulse radiolysis ; Tunneling
• 刊名：Inorganica Chimica Acta
• 出版年：1996
• 出版时间：February 29, 1996
• 年：1996
• 卷：243
• 期：1-2
• 页码：127-133
• 全文大小：630 K

文摘

Long range electron transfer (LRET) can be induced between the disulfide radical anion, produced pulse radiolytically, and the copper(II) center in the single blue copper protein, azurin. The rate constant of this intramolecular process increases by one order of magnitude upon decreasing the pH from 8 to 4 in all azurins (wild types as well as single site mutants of Pseudomonas aeruginosa azurin) studied so far. In order to pursue the structural basis for the observed pH dependence we have extended our studies to a new mutant, Asp23Ala. In this derivative the aspartate residue is proximal to the electron donating cystine disulfide bridge. However, LRET in this azurin was found to exhibit similar pH dependence as all other wild type and single-site mutants with residues potentially being able to affect the electron transfer process. A detailed consideration of the parameters that determine the efficiency of this process leads to the suggestion that a pH induced change either in the electron transfer distance or in the electronic coupling may be the cause of this behavior.