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The function of holocytochrome c synthase (HCCS, also called heme lyase) is to attach covalently the heme cofactor to cytochromes c in the mitochondria of animals, fungi and protozoa. Little is known about how the protein functions but CP motifs, commonly found in heme-binding proteins, are present. Here we examine holocytochrome c production by Saccharomyces cerevisiae HCCS in the Escherichia coli cytoplasm with emphasis on the conserved CP motifs long implicated in heme transfer by this enzyme. Unexpectedly, the two motifs, both towards the N-terminus, were not required for activity. Mutations in HCCS on the C-terminal side of the CP motifs, known to cause disease states in humans (microphthalmia with linear skin defects) abolished or drastically attenuated holocytochrome c production.

Original publication




Journal article



Publication Date





3415 - 3419


Amino Acid Motifs, Amino Acid Sequence, Animals, Conserved Sequence, Cytochromes c, Heme, Humans, Lyases, Mice, Mitochondria, Mitochondrial Diseases, Molecular Sequence Data, Mutation, Protein Binding, Saccharomyces cerevisiae