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Role of Elongation Factor G and a Protein Factor on the Release of Ribosomes from Messenger Ribonucleic Acid

1973; Elsevier BV; Volume: 248; Issue: 21 Linguagem: Inglês

10.1016/s0021-9258(19)43330-9

1083-351X

Akikazu Hirashima, Akira Kaji,

Viral Infections and Immunology Research

Abstract The process of ribosome run-off from messenger RNA in the presence of puromycin, elongation factor G and an additional factor was further studied. Formation of run-off ribosomes (release of ribosomes) from naturally occurring polysomes was measured by following the conversion of polysomes into 70 S ribosomes. The optimum concentrations of Mg2+ and NH4+ for this process were 5 to 8 mm and 70 to 80 mm, respectively. Fusidic acid and sparsomycin were inhibitory. Since sparsomycin has been found to inhibit the release of the nascent polypeptide from the ribosome in the presence of puromycin, it was postulated that the substrate for this enzymatic release of ribosomes would be the complex of messenger RNA, ribosome, and unesterified transfer RNA. For the release of ribosomes from this complex, the simultaneous presence of elongation factor G, GTP, and the additional factor were necessary. The release of ribosomes from messenger RNA was accompanied by the simultaneous release of transfer RNA from ribosomes. The 70 S ribosomes released from messenger RNA were further dissociated into their subunits (30 S and 50 S) by the presence of initiation factor three. These ribosomes were biologically active in a MS2 phage RNA-dependent amino acid incorporation system. These observations support the hypothesis that elongation factor G and an additional factor play a role in the process of ribosome run-off from messenger RNA at the end of the cistron or abortively at the middle of the cistron.