Bacterial genes and proteins involved in the biogenesis of c-type cytochromes and terminal oxidases.

A total of nine genes potentially concerned with the biosynthesis of c-type cytochromes have been identified recently in the bacteria Bradyrhizobium japonicum and Rhodobacter capsulatus, and homologous counterparts appear to be present also in Escherichia coli. Most of the respective gene products are membrane-bound, while others are located in the periplasmic space. As inferred from sequence analyses, several of these proteins may play roles in membrane transport or redox processes, both functions being consistent with the required steps in cytochrome c formation (membrane translocation of heme; covalent linkage of protoheme IX to cysteine thiols). Further genes of B. japonicum, E. coli, Bacillus subtilis and Paracoccus denitrificans have been studied whose products are necessary for the formation of intact heme/copper oxidases. Some of them are probably required in protein folding and assembly whereas others appear to be enzymes catalyzing steps in the biosynthesis of the heme cofactors.