TITLE

A functional description of CymA, an electron-transfer hub supporting anaerobic respiratory flexibility in Shewanella

AUTHOR(S)
MARRITT, Sophie J.; LOWE, Thomas G.; BYE, Jordan; MCMILLAN, Duncan G. G.; Liang SHI; FREDRICKSON, Jim; ZACHARA, John; RICHARDSON, David J.; CHEESMAN, Myles R.; JEUKEN, Lars J. C.; BUTT, Julea N.
PUB. DATE
June 2012
SOURCE
Biochemical Journal;6/15/2012, Vol. 444 Issue 3, p465
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
CymA (tetrahaem cytochrome c) is a member of the NapC/NirT family of quinol dehydrogenases. Essential for the anaerobic respiratory flexibility of shewanellae, CymA transfers electrons from menaquinol to various dedicated systems for the reduction of terminal electron acceptors including fumarate and insoluble minerals of Fe(III). Spectroscopic characterization of CymA from Shewanella oneidensis strain MR-1 identifies three lowspin His/His co-ordinated c-haems and a single high-spin chaem with His/H2O co-ordination lying adjacent to the quinolbinding site. At pH 7, binding of the menaquinol analogue, 2-heptyl-4-hydroxyquinoline-N-oxide, does not alter the midpoint potentials of the high-spin (approximately -240 mV) and low-spin (approximately -110, -190 and -265 mV) haems that appear based to transfer electrons from the high- to lowspin centres following quinol oxidation. CymA is reduced with menadiol (Em= -80 mV) in the presence ofNADH(Em= -320 mV) and an NADH-menadione (2-methyl-1,4-naphthoquinone) oxidoreductase, but not by menadiol alone. In cytoplasmic membranes reduction of CymA may then require the thermodynamic driving force from NADH, formate or H2 oxidation as the redox poise of the menaquinol pool in isolation is insufficient. Spectroscopic studies suggest that CymA requires a non-haem co-factor for quinol oxidation and that the reduced enzyme forms a 1:1 complex with its redox partner Fcc3 (flavocytochrome c3 fumarate reductase). The implications for CymA supporting the respiratory flexibility of shewanellae are discussed.
ACCESSION #
85236257

 

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics