Distinct epitopes in eukaryotic initiation factor 2 for binding of mRNA and for ternary complex formation with methionyl-tRNA(f) and GTP.
Eukaryotic initiation factor 2 (eIF-2) forms a ternary complex with methionyl-tRNA(fMet) and GTP on one hand, and it binds to a specific site in mRNA molecules on the other. Antibodies directed against eIF-2 were used to analyze these dual binding activities. A monoclonal antibody directed against the beta-subunit of eIF-2, 5A4, is able to inhibit ternary complex formation as well as binding of mRNA, showing that this subunit is essential for both binding activities of eIF-2. However, a polyclonal antibody, PR1, is able to distinguish between these activities in the eIF-2 molecule. In the presence of PR1, binding of mRNA by eIF-2 is inhibited completely, yet ternary complex formation with methionyl-tRNA(fMet) and GTP is stimulated more than 5-fold. Apparently, specific antibodies to eIF-2 can induce a conformational change in inactive factor molecules that permits them to form ternary complexes. These results show that distinct epitopes in eIF-2 are involved in binding of mRNA and in ternary complex formation with methionyl-tRNA(fMet) and GTP.
Department of Molecular Virology, Hebrew University, Hadassah Medical School, Jerusalem, Israel.
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Kaempfer
D000818:Animals; D000906:Antibodies; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D001665:Binding Sites; D000939:Epitopes / Q000032:analysis; D015852:Eukaryotic Initiation Factor-2 / Q000276:immunology / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012358:RNA, Transfer, Met; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism
D000906:Antibodies; D000911:Antibodies, Monoclonal; D000939:Epitopes; D015852:Eukaryotic Initiation Factor-2; D046911:Macromolecular Substances; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; D012358:RNA, Transfer, Met; C024988:tRNA, formylmethionine-; D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate