Activation volumes for intramolecular electron transfer in bovine heart cytochrome c oxidase

FEBS Letters

Larsen, Randy W¹ 

[1] Department of Chemistry, University of Hawaii at Manoa, 2545 The Mall, Honolulu, HI 96822, USA

关键词: High pressure;    Cytochrome oxidase;    Electron transfer;    Activation volume;   

DOI  :  10.1016/S0014-5793(99)01517-3

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The present work examines the activation volumes associated with intramolecular electron transfer (ET) within the CO-mixed-valence form of bovine heart cytochrome c oxidase (CcO). Activation volumes for intramolecular ET between cytochrome a ₃ and cytochrome a (k=(6.7±0.9)×10⁵ s⁻¹ at ambient pressure) and between cytochrome a and Cu_A (k=(5.9±1.7)×10⁴ s⁻¹) are found to be +41±5 ml/mol and +28±4 ml/mol, respectively. Examination of the crystal structures of both the fully oxidized and fully reduced forms of bovine heart CcO suggest that the activation volume for the ET between cytochrome a ₃ and cytochrome a arises from structural changes localized at cytochrome a ₃ upon heme reduction. Similarly, the activation volume for the ET between cytochrome a and Cu_A is primarily due to structural changes localized at Cu_A upon reduction of this site. Reduction/oxidation of cytochrome a does not appear to make any significant contribution to the activation volume. Overall, these results suggest conformational regulation of ET by both Cu_A and cytochrome a ₃ but not cytochrome a.

【 授权许可】

Unknown