Site-directed mutagenesis of the histidine heme ligand in iso-1-cytochrome c of Saccharomyces cerevisiae

The invariant heme axial ligand, histidine-18, of yeast iso-2-cytochrome c has been replaced with arginine via site-directed mutagenesis. Yeast that overexpress this variant protein can grow on nonfermentable carbon sources, albeit more slowly than yeast containing the wild-type protein. This means that electron transport has not been eliminated by the mutation. However, it is not known if the guanidyl group of arginine is ligating the heme iron.