Activation volumes for intramolecular electron transfer in Escherichia coli cytochrome bo3

FEBS Letters

Gennis, Robert B²  Ching, Erin¹  Larsen, Randy W¹ 

[1] University of Hawaii at Manoa, Department of Chemistry, 2545 The Mall, Honolulu, HI 96822, USA;University of Illinois-Urbana, School of Chem. Sciences, 600 South Mathews Ave. Urbana, IL 61801, USA

关键词: High pressure;    Cytochrome bo3;    Cytochrome c oxidase;    Electron transfer;    Mixed valence;    Activation volume;   

DOI  :  10.1016/S0014-5793(02)03170-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

In this report we describe the activation volumes associated with the heme–heme electron transfer (ET) and CO rebinding to the binuclear center subsequent to photolysis of the CO-mixed-valence derivative of Escherichia coli cytochrome bo₃ (Cbo). The activation volumes associated with the heme–heme ET (k=1.2×10⁵ s⁻¹), and CO rebinding (k=57 s⁻¹) are found to be +27.4 ml/mol and −2.6 ml/mol, respectively. The activation volume associated with the rebinding of CO is consistent with previous Cu X-ray absorption studies of Cbo where a structural change was observed at the Cu_B site (loss of a histidine ligand) due to a change in the redox state of the binuclear center. In addition, the volume of activation for the heme–heme ET was found to be quite distinct from the activation volumes obtained for heme–heme ET in bovine heart Cytochrome c oxidase. Differences in mechanisms/pathways for heme b/heme o₃ and heme a/heme a₃ ET are suggested based on the associated activation volumes and previously obtained Marcus parameters.

【 授权许可】

Unknown