Interaction of mitochondrial initiation factor 2 with mitochondrial fMet-tRNA.
The mammalian mitochondrial genome contains a single tRNA(Met) gene that gives rise to the initiator and elongator tRNA(Met). It is generally believed that mitochondrial protein synthesis begins with formylmethionyl-tRNA, which indicates that the formylation of mitochondrial Met-tRNA specifies its participation in initiation through its interaction with initiation factor 2 (IF-2). However, recent studies in yeast mitochondria, suggest that formylation is not required for protein synthesis. In addition, bovine IF-2(mt) could replace yeast IF-2(mt) in strains that lack fMet-tRNA which suggests that this paradigm may extend to mammalian mitochondria. Here, the importance of the formylation of mitochondrial Met-tRNA for the interaction with IF-2(mt) was investigated by measuring the ability of bovine IF-2(mt) to bind mitochondrial fMet-tRNA. In direct binding experiments, bovine IF-2(mt) has a 25-fold greater affinity for mitochondrial fMet-tRNA than Met-tRNA, using either the native mitochondrial tRNA(Met) or an in vitro transcript of bovine mitochondrial tRNA(Met). In addition, IF-2(mt) will not effectively stimulate mitochondrial Met-tRNA binding to mitochondrial ribosomes, exhibiting a 50-fold preference for fMet-tRNA over Met-tRNA in this assay. Finally, the region of IF-2(mt) responsible for the interaction with fMet-tRNA was mapped to the C2 sub-domain of domain VI of this factor.
Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290, USA.
Angela C
AC
Spencer
Linda L
LL
Spremulli
D000818:Animals; D002417:Cattle; D039642:Eukaryotic Initiation Factors / Q000378:metabolism*; D019877:Hydroxymethyl and Formyl Transferases / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000096:biosynthesis; D010442:Peptide Chain Initiation, Translational; D012313:RNA / Q000378:metabolism*; D000077278:RNA, Mitochondrial; D012358:RNA, Transfer, Met / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
D039642:Eukaryotic Initiation Factors; C451339:IFM1 protein, S cerevisiae; D024101:Mitochondrial Proteins; D000077278:RNA, Mitochondrial; D012358:RNA, Transfer, Met; D029701:Saccharomyces cerevisiae Proteins; C024988:tRNA, formylmethionine-; D012313:RNA; D019877:Hydroxymethyl and Formyl Transferases; C021561:methionyl-tRNA formyltransferase