A MUTATION BLOCKING THE FORMATION OF MEMBRANE OR PERIPLASMIC ENDOGENOUS AND EXOGENOUS C-TYPE CYTOCHROMES IN ESCHERICHIA-COLI PERMITS THE CYTOPLASMIC FORMATION OF HYDROGENOBACTER-THERMOPHILUS HOLE CYTOCHROME-C(552)

A mutant of Escherichia coli, JCB606, shown to be pleiotropically defi cient in the formation of endogenous membrane and periplasmic c-type c ytochromes, synthesised the apo form of the exogenous cytochrome c(550 ) from Paracoccus denitrificans, but not the holo form. In contrast, a cytoplasmically located hole form of Hydrogenobacter thermophilus cyt ochrome c(552) was found in E. coli JCB606. These findings support the proposition that the formation of the cytoplasmic H. thermophilus cyt ochrome c(552) in E. coli does not involve the physiological pathway o f c-type cytochrome biosynthesis in E. coli and that the haem insertio n may be uncatalysed.