title: Complementation of a yeast CYC3 deficiency identifies an X-linked mammalian activator of apocytochrome c.
abstract: We have shown by indirect immunofluorescence and enhanced green fluorescent protein fusions that a mammalian sequence exhibiting similar levels of homology to the two yeast heme lyases Cyc3p (holocytochrome c synthase; HCCS) and Cyt2p (holocytochrome c1 synthase; HCC1S) is also targeted to mitochondria. The human protein was able to complement the yeast Cyc3p (but not Cyt2p) deficiency, which indicates that it specifically activates apocytochrome c. Consistent with a respiratory role, expression of the mammalian gene was detected in all tissues, with the highest levels found in heart. Notably, the human gene HCCS is the only known gene located within the critical region for the deletion-defined disorder microphthalmia with linear skin defects (MLS). We believe the spectrum of clinical features seen in females with MLS and the paucity of male patients are consistent with significant involvement of HCCS. Toward clarification of a role for HCCS in disease, we have extensively characterized the X-linked mouse Hccs genomic locus, showing conservation in gene size and arrangement despite its location in a region that has undergone significant evolutionary rearrangement.
authors.affiliation: Department of Molecular Biosciences and Centre for the Molecular Genetics of Development, University of Adelaide, North Terrace, Adelaide, South Australia, Australia 5005.
authors.forename: Quenten P
authors.initials: QP
authors.lastname: Schwarz
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Cox
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001059:Apoproteins / Q000378:metabolism*; D019556:COS Cells; D003574:Cytochrome c Group / Q000378:metabolism*; D045304:Cytochromes c; D020536:Enzyme Activators / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D008040:Genetic Linkage; D006367:HeLa Cells; D006801:Humans; D008190:Lyases / Q000235:genetics* / Q000378:metabolism; D008297:Male; D051379:Mice; D008850:Microphthalmos / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D016415:Sequence Alignment; D017385:Sequence Homology; D014960:X Chromosome / Q000235:genetics
chemical_list: D001059:Apoproteins; D003574:Cytochrome c Group; D020536:Enzyme Activators; D024101:Mitochondrial Proteins; D045304:Cytochromes c; D008190:Lyases; C031581:cytochrome C synthetase