Overproduction of theBradyrhizobium japonicum c-Type Cytochrome Subunits of thecbb3Oxidase inEscherichia coli

We report on a system to improve expression of maturec-type cytochromes inEscherichia coli.It is based on the use of plasmid pEC86 that expresses theE. colicytochromecmaturation genesccmABCDEFGHconstitutively, whereby the production of both endogenous and foreignc-type cytochromes was increased substantially. The periplasmic soluble domains of thec-type cytochrome subunits FixO and FixP of theBradyrhizobium japonicum cbb3oxidase could be expressed inE. colionly when pEC86 was provided in adegP-deficient strain. This shows that a stimulation of heme attachment by the Ccm maturase system combined with the diminished proteolytic activity in the periplasm can increasec-type cytochrome yields.