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Activation volumes for intramolecular electron transfer in Escherichia coli cytochrome bo 3
Author(s) -
Ching Erin,
Gennis Robert B,
Larsen Randy W
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)03170-8
Subject(s) - heme , chemistry , heme a , cytochrome , electron transfer , hemeprotein , photochemistry , cytochrome c , histidine , carbon monoxide , photodissociation , stereochemistry , biochemistry , enzyme , catalysis , mitochondrion
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 bo 3 (Cbo). The activation volumes associated with the heme–heme ET ( k =1.2×10 5 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 o 3 and heme a /heme a 3 ET are suggested based on the associated activation volumes and previously obtained Marcus parameters.