title: Functional analysis of the domains in Cox11.
abstract: Cox11 is an intrinsic mitochondrial membrane protein essential for the assembly of an active cytochrome c oxidase complex. Cox11 is tethered to the mitochondrial inner membrane by a single transmembrane helix. Domain mapping was carried out to determine the functional segments of the Cox11 protein. The C-terminal 189 residue Cu(I)-binding domain is shown to be exposed within the mitochondrial intermembrane space. This orientation was demonstrated by the proteolytic susceptibility of a C-terminal Myc epitope tag in mitoplasts but not intact mitochondria. Fusion of the N terminus of Cox11 to the matrix ribosomal protein Rsm22 results in a functional protein capable of suppressing the respiratory defect of both Deltacox11 cells and Deltarsm22 cells. The functionality of the fusion protein suggests that the Cox11 N terminus projects into the matrix. The fusion of the C-terminal segment of Cox11 to Rsm22 resembles a naturally occurring fusion of Cox11 in Schizosaccharomyces pombe to a sequence homologous to the Saccharomyces cerevisiae Rsm22. Studies on a series of SCO1/COX11 chimeras reveal that the matrix domain of Cox11 lacks a specific function, whereas the Cu(I) binding/donating function requires the yeast Cox11 sequence. The Cu(I)-binding domain from human Cox11 cannot functionally replace the yeast sequence. The copper domain of Cox11 may be an important docking motif for Cox1 or a Cox1-associated protein.
authors.affiliation: University of Utah Health Sciences Center, Salt Lake City, 84132, USA.
authors.forename: Heather S
authors.initials: HS
authors.lastname: Carr
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Maxfield
authors.forename: Yih-Chern
authors.initials: YC
authors.lastname: Horng
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Winge
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000939:Epitopes / Q000737:chemistry; D005816:Genetic Complementation Test; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000737:chemistry* / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016271:Proto-Oncogene Proteins c-myc / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012269:Ribosomal Proteins / Q000737:chemistry*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000502:physiology*; D012568:Schizosaccharomyces / Q000201:enzymology*; D014357:Trypsin / Q000494:pharmacology
chemical_list: C086106:COX11 protein, S cerevisiae; D000939:Epitopes; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D016271:Proto-Oncogene Proteins c-myc; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; C502078:Rsm22 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014357:Trypsin