The role of multihaem cytochromes in the respiration of nitrite in Escherichia coli and Fe(III) in Shewanella oneidensis

Authors

Thomas A. Clarke, University of East AngliaFollow
Tracey Holley, University of East Anglia
Robert S. Hartshorne, University of East Anglia
James K. Fredrickson, Pacific Northwest National LaboratoryFollow
John M. Zachara, Pacific Northwest National LaboratoryFollow
Liang Shi, Pacific Northwest National LaboratoryFollow
David J. Richardson, University of East AngliaFollow

Date of this Version

2008

Citation

Biochem. Soc. Trans. (2008) 36, 1005–1010; doi:10.1042/BST0361005

Abstract

The periplasmic nitrite reductase system from Escherichia coli and the extracellular Fe (III) reductase system from Shewanella oneidensis contain multihaem c-type cytochromes as electron carriers and terminal reductases. The position and orientation of the haem cofactors in multihaem cytochromes from different bacteria often show significant conservation despite different arrangements of the polypeptide chain. We propose that the decahaem cytochromes of the iron reductase system MtrA, MtrC and OmcA comprise pentahaem ‘modules’ similar to the electron donor protein, NrfB, from E. coli. To demonstrate this, we have isolated and characterized the N-terminal pentahaem module of MtrA by preparing a truncated form containing five covalently attached haems. UV–visible spectroscopy indicated that all five haems were low-spin, consistent with the presence of bis-His ligand co-ordination as found in full-length MtrA.