Portal de Periódicos da CAPES

Characterization of the Interaction of Aminoacyltransferase II with Ribosomes

1968; Elsevier BV; Volume: 243; Issue: 20 Linguagem: Inglês

10.1016/s0021-9258(18)91956-3

1083-351X

Lawrence Skogerson, Kivie Moldave,

Radiopharmaceutical Chemistry and Applications

Abstract When ribosomes are incubated with transferase II, guanosine triphosphate, and a sulfhydryl compound, ribosomes can be isolated which carry out aminoacyl transfer in the presence of transferase I, 14C-aminoacyl transfer ribonucleic acid, and GTP, but in the absence of added transferase II. The initial rate of aminoacyl transfer with isolated ribosome-transferase II complex is markedly stimulated compared to that with nonpreincubated ribosomes. Binding of transferase II to ribosomes can be obtained with GTP at 4°, or with 5'-guanylyl methylenediphosphonate or GDP at 37°; however, under these conditions, the initial rates of aminoacyl transfer with isolated ribosome-transferase II complex are not stimulated unless the complex is incubated briefly with GTP prior to the aminoacyl transfer reaction. The kinetics exhibited by the ribosome-transferase II complex formed in the presence of GTP at 37° appears to be due to the priming of ribosomes for the rapid acceptance of the incoming aminoacyl-tRNA; this process could reflect translocation of endogenous peptidyl-tRNA from the aminoacyl to the peptidyl site, making additional sites available for the binding and incorporation of aminoacyl-tRNA. Binding of transferase II to ribosomes and the translocation reaction are two distinct steps that can be dissociated from each other. The formation of ribosome-transferase II complex can be obtained in the absence of translocation. If translocation is allowed to occur, an aminoacyl-tRNA can be bound in the presence of transferase I, and a peptide bond can be formed, even after removal of the bound transferase II from the ribosome.