Characterization of axial and proximal histidine mutations of the decaheme cytochrome MtrA from Shewanella sp. strain ANA-3 and implications for the electron transport system.

Extracellular respiration of solid-phase electron acceptors in some microorganisms requires a complex chain of multiheme c-type cytochromes that span the inner and outer membranes. In Shewanella species, MtrA, an ~35-kDa periplasmic decaheme c-type cytochrome, is an essential component for extracellular respiration of iron(III). The exact mechanism of electron transport has not yet been resolved, but the arrangement of the polypeptide chain may have a strong influence on the capability of the MtrA cytochrome to transport electrons.