title: The interaction of mitochondrial translational initiation factor 2 with the small ribosomal subunit.
abstract: Bovine mitochondrial translational initiation factor 2 (IF-2(mt)) is organized into four domains, an N-terminal domain, a central G-domain and two C-terminal domains. These domains correspond to domains III-VI in the six-domain model of Escherichia coli IF-2. Variants in IF-2(mt) were prepared and tested for their abilities to bind the small (28S) subunit of the mitochondrial ribosome. The binding of wild-type IF-2(mt) was strong (K(d) approximately 10-20 nM) and was not affected by fMet-tRNA. Deletion of the N-terminal domain substantially reduced the binding of IF-2(mt) to 28S subunits. However, the addition of fMet-tRNA stimulated the binding of this variant at least 2-fold demonstrating that contacts between fMet-tRNA and IF-2(mt) can stabilize the binding of this factor to 28S subunits. No binding was observed for IF-2(mt) variants lacking the G-domain which probably plays a critical role in organizing the structure of IF-2(mt). IF-2(mt) contains a 37-amino acid insertion region between domains V and VI that is not found in the prokaryotic factors. Mutations in this region caused a significant reduction in the ability of the factor to promote initiation complex formation and to bind 28S subunits.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA.
authors.forename: Angela C
authors.initials: AC
authors.lastname: Spencer
authors.forename: Linda L
authors.initials: LL
authors.lastname: Spremulli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002417:Cattle; D004926:Escherichia coli / Q000235:genetics; D006150:Guanine Nucleotides / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D039881:Prokaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012339:RNA, Ribosomal, 28S / Q000378:metabolism*; D012358:RNA, Transfer, Met / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D006150:Guanine Nucleotides; D024101:Mitochondrial Proteins; D039881:Prokaryotic Initiation Factor-2; D012339:RNA, Ribosomal, 28S; D012358:RNA, Transfer, Met; D011994:Recombinant Proteins; C024988:tRNA, formylmethionine-