MOLECULAR-BIOLOGY OF C-TYPE CYTOCHROMES FROM DESULFOVIBRIO-VULGARIS HILDENBOROUGH

Sulfate reducing bacteria of the genus Desulfovibrio harbor a wide variety of redox proteins. Three different c-type cytochromes, cytochrome c-553, cytochrome c(3) and the high molecular mass cytochrome have been isolated from these bacteria. The high molecular mass cytochrome is part of an operon that encodes a transmembrane protein complex that mediates electron transfer across the cytoplasmic membrane. The physiological function of the other two cytochromes is less clear. They are encoded by monocistronic genes and their redox partners can thus not be identified by gene sequencing. Expression of genes for c-type cytochromes in a foreign host art complicated due to the requirement for covalent heme insertion. Cytochrome c-553 is readily expressed in Escherichia coli in funtional form, but cytochrome c(3) and the high molecular mass cytochrome are not for reasons that are presently not clear.