title: Mitochondrial ferredoxin is required for heme A synthesis in Saccharomyces cerevisiae.
abstract: Heme A is a prosthetic group of all eukaryotic and some prokaryotic cytochrome oxidases. This heme differs from heme B (protoheme) at two carbon positions of the porphyrin ring. The synthesis of heme A begins with farnesylation of the vinyl group at carbon C-2 of heme B. The heme O product of this reaction is then converted to heme A by a further oxidation of a methyl to a formyl group on C-8. In a previous study (Barros, M. H., Carlson, C. G., Glerum, D. M., and Tzagoloff, A. (2001) FEBS Lett. 492, 133-138) we proposed that the formyl group is formed by an initial hydroxylation of the C-8 methyl by a three-component monooxygenase consisting of Cox15p, ferredoxin, and ferredoxin reductase. In the present study three lines of evidence confirm a requirement of ferredoxin in heme A synthesis. 1) Temperature-conditional yah1 mutants grown under restrictive conditions display a decrease in heme A relative to heme B. 2) The incorporation of radioactive delta-aminolevulinic acid into heme A is reduced in yah1 ts but not in the wild type after the shift to the restrictive temperature; and 3) the overexpression of Cox15p in cytochrome oxidase mutants that accumulate heme O leads to an increased mitochondrial concentration of heme A. The increase in heme A is greater in mutants that overexpress Cox15p and ferredoxin. These results are consistent with a requirement of ferredoxin and indirectly of ferredoxin reductase in hydroxylation of heme O.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
authors.forename: Mario H
authors.initials: MH
authors.lastname: Barros
authors.forename: Francisco G
authors.initials: FG
authors.lastname: Nobrega
authors.forename: Alexander
authors.initials: A
authors.lastname: Tzagoloff
mesh_terms: D000325:Adrenodoxin; D000622:Aminolevulinic Acid / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005288:Ferredoxins / Q000378:metabolism* / Q000502:physiology*; D005656:Fungal Proteins / Q000235:genetics; D006418:Heme / Q000031:analogs & derivatives* / Q000096:biosynthesis* / Q000378:metabolism; D006900:Hydroxylation; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D013997:Time Factors
chemical_list: C107633:COX15 protein, S cerevisiae; D005288:Ferredoxins; D005656:Fungal Proteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C120375:YAH1 protein, S cerevisiae; D000325:Adrenodoxin; C069808:heme O; C027728:heme a; D006418:Heme; D000622:Aminolevulinic Acid; D003576:Electron Transport Complex IV