Activity of Euglena gracilis chloroplast ribosomes with procaryotic and eucaryotic initiation factors.
A method that permits the preparation of Euglena gracilis chloroplast 30 S ribosomal subunits that are largely free of endogenous initiation factors and that are active in the binding of fMet-tRNA in response to poly(A, U, G), has been developed. These 30 S subunits have been tested for activity in initiation complex formation with initiation factors from both procaryotes and eucaryotes. We have observed that Escherichia coli IF-2 binds fMet-tRNA nearly as well to Euglena chloroplast ribosomal subunits as it does to its homologous subunits. Neither wheat germ eIF-2 nor Euglena eIF-2A can bind fMet-tRNA efficiently to Euglena chloroplast or E. coli 30 S subunits although both are active with wheat germ 40 S ribosomal subunits. Euglena chloroplast 68 S ribosomes will also bind the initiator tRNA. Both E. coli IF-2 and E. coli IF-3 stimulate this reaction on chloroplast ribosomes with approximately the same efficiency as they do on their homologous ribosomes. E. coli IF-1 enhances the binding of fMet-tRNA to the chloroplast 68 S ribosomes when either IF-2 or IF-3 is limiting. The chloroplast ribosomes unlike E. coli ribosomes show considerable activity over a broad range of Mg2+ ion concentrations.
D001665:Binding Sites; D002736:Chloroplasts / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D005056:Euglena gracilis / Q000378:metabolism; D005057:Eukaryotic Cells / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism*; D011387:Prokaryotic Cells / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012358:RNA, Transfer, Met; D012270:Ribosomes / Q000378:metabolism*
D010448:Peptide Initiation Factors; D012346:RNA, Transfer, Amino Acyl; D012358:RNA, Transfer, Met; C024988:tRNA, formylmethionine-