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

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