title: Interactions among three proteins that specifically activate translation of the mitochondrial COX3 mRNA in Saccharomyces cerevisiae.
abstract: The PET54, PET122, and PET494 proteins, which are associated with the yeast inner mitochondrial membrane, specifically activate translation of the mitochondrially encoded COX3 mRNA. We used the two-hybrid system to test whether pairs of these proteins, when fused to either the GAL4 DNA-binding or transcriptional activating domain, can physically associate as measured by the expression of the GAL4-dependent reporter, lacZ. PET54 and PET122 interacted in this system, and an amino-terminally truncated PET494 fragment showed an interaction with PET54. We also detected functional interactions between PET54 and PET122 genetically: a pet54 missense substitution (Phe to Gly at position 244) that caused a severe respiratory defect was suppressed both by a missense substitution affecting PET122 (Gly to Val at position 211) and by overproduction of wild-type PET122. Both Gly and Ala, substituted at PET54 position 244, disrupted the two-hybrid interactions with PET122 and PET494. While Ala at PET54 position 244 caused only a modest respiratory phenotype alone, it caused a severe respiratory defect when combined with a cold-sensitive mitochondrial mutation affecting the COX3 mRNA 5' leader. This synthetic defect was suppressed by a missense substitution in PET122 and by overproduction of wild-type PET122, indicating functional interactions among PET54, PET122, and the mRNA. Taken together with previous work, these data suggest that a complex containing PET54, PET122, and PET494 mediates the interaction of the COX3 mRNA with mitochondrial ribosomes at the surface of the inner membrane.
authors.affiliation: Section of Genetics and Development, Cornell University, Ithaca, New York 14853-2703.
authors.forename: N G
authors.initials: NG
authors.lastname: Brown
authors.forename: M C
authors.initials: MC
authors.lastname: Costanzo
authors.forename: T D
authors.initials: TD
authors.lastname: Fox
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D003576:Electron Transport Complex IV / Q000096:biosynthesis*; D005656:Fungal Proteins / Q000096:biosynthesis / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D016153:Genes, Suppressor; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D017931:DNA Primers; D005656:Fungal Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D003576:Electron Transport Complex IV