title: The Assembly Factor Pet117 Couples Heme a Synthase Activity to Cytochrome Oxidase Assembly.
abstract: Heme a is an essential metalloporphyrin cofactor of the mitochondrial respiratory enzyme cytochrome c oxidase (CcO). Its synthesis from heme b requires several enzymes, including the evolutionarily conserved heme a synthase (Cox15). Oligomerization of Cox15 appears to be important for the process of heme a biosynthesis and transfer to maturing CcO. However, the details of this process remain elusive, and the roles of any additional CcO assembly factors that may be involved remain unclear. Here we report the systematic analysis of one such uncharacterized assembly factor, Pet117, and demonstrate in Saccharomyces cerevisiae that this evolutionarily conserved protein is necessary for Cox15 oligomerization and function. Pet117 is shown to reside in the mitochondrial matrix, where it is associated with the inner membrane. Pet117 functions at the later maturation stages of the core CcO subunit Cox1 that precede Cox1 hemylation. Pet117 also physically interacts with Cox15 and specifically mediates the stability of Cox15 oligomeric complexes. This Cox15-Pet117 interaction observed by co-immunoprecipitation persists in the absence of heme a synthase activity, is dependent upon Cox1 synthesis and early maturation steps, and is further dependent upon the presence of the matrix-exposed, unstructured linker region of Cox15 needed for Cox15 oligomerization, suggesting that this region mediates the interaction or that the interaction is lost when Cox15 is unable to oligomerize. Based on these findings, it was concluded that Pet117 mediates coupling of heme a synthesis to the CcO assembly process in eukaryotes.
authors.affiliation: From the Department of Chemistry and Biochemistry, College of Charleston, Charleston, South Carolina 29424.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Taylor
authors.affiliation: the Department of Biochemistry and Nebraska Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588.
authors.forename: Samantha
authors.initials: S
authors.lastname: Swenson
authors.affiliation: From the Department of Chemistry and Biochemistry, College of Charleston, Charleston, South Carolina 29424.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Harris
authors.affiliation: the Department of Biochemistry and Nebraska Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588.
authors.forename: Edward M
authors.initials: EM
authors.lastname: Germany
authors.affiliation: From the Department of Chemistry and Biochemistry, College of Charleston, Charleston, South Carolina 29424. Electronic address: foxjl@cofc.edu.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Fox
authors.affiliation: the Department of Biochemistry and Nebraska Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588. Electronic address: okhalimonchuk2@unl.edu.
authors.forename: Oleh
authors.initials: O
authors.lastname: Khalimonchuk
mesh_terms: D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D005294:Ferrochelatase / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C107633:COX15 protein, S cerevisiae; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C526453:Cox1 protein, S cerevisiae; D003576:Electron Transport Complex IV; D005294:Ferrochelatase
keywords: Cox15; Pet117; cytochrome c oxidase (Complex IV); heme; mitochondria; mitochondrial disease; oligomerization