Identification of ribosome-bound eukaryotic initiation factor 2.GDP binary complex as an intermediate in polypeptide chain initiation reaction.
Studies on the formation and release of the eukaryotic initiation factor (eIF)-2.GDP binary complex formed during eIF-5-mediated assembly of an 80 S initiation complex have been carried out. Incubation of a 40 S initiation complex with eIF-5, in the presence or absence of 60 S ribosomal subunits at 25 degrees C, causes rapid and quantitative hydrolysis of ribosome-bound GTP to form an eIF-2.GDP binary complex and Pi. Analysis of both reaction products by Sephadex G-200 gel filtration reveals that while Pi is released from ribosomes, the eIF-2.GDP complex remains bound to the ribosomal initiation complex. The eIF-2.GDP binary complex can however be released from ribosome by subjecting the eIF-5-catalyzed reaction products to either longer periods of incubation at 37 degrees C or sucrose gradient centrifugation. Furthermore, addition of a high molar excess of isolated eIF-2.GDP binary complex to a 40 S initiation reaction mixture does not cause exchange of ribosome-bound eIF-2.GDP complex formed by eIF-5-catalyzed hydrolysis of GTP. These results indicate that eIF-2.GDP complex is directly formed on the surface of ribosomes following hydrolysis of GTP bound to a 40 S initiation complex, and that ribosome-bound eIF-2 X GDP complex is an intermediate in polypeptide chain initiation reaction.
Raychaudhuri
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Maitra
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D000818:Animals; D002417:Cattle; D002499:Centrifugation, Density Gradient; D015852:Eukaryotic Initiation Factor-2; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*
D015852:Eukaryotic Initiation Factor-2; D006150:Guanine Nucleotides; D010448:Peptide Initiation Factors; D011506:Proteins; D006153:Guanosine Diphosphate