A tetraheme cytochrome c was successfully overexpressed for the first time in Escherichia coli. Desulfovibrio desulfuricans ATCC 27774 tetraheme cytochrome cg was expressed in aerobically grown Escherichia coli cotransformed with Escherichia coli ccm gene cluster (Arslan et al. (1998) Bioch. Biophys. Res. Commun. 251, 744-747). The analysis of the produced cytochrome showed that the signal peptide was correctly cleaved, the four heme groups were inserted and the electronic structure around the heme irons was conserved, i.e., the recombinant tetraheme cytochrome was identical to that isolated from the native source. Contradicting previous results which indicated that Escherichia coli was only capable of producing apocytochrome c, (Pollock et al. (1989) J. Gen. Microbiol. 135, 2319-2328), the present work proves unequivocally that the holoform can also be obtained,