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. 1974 Dec;71(12):4950–4954. doi: 10.1073/pnas.71.12.4950

Effect of Initiation Factor 3 Binding on the 30S Ribosomal Subunits of Escherichia coli*

Cynthia L Pon 1, Claudio Gualerzi 1
PMCID: PMC434017  PMID: 4612534

Abstract

Under certain conditions, initiation factor 3 (IF-3) can cause the release of aminoacyl-tRNA bound to 30S ribosomal subunits of E. coli. It is shown that this IF-3-induced aminoacyl-tRNA release cannot be attributed to either nucleolytic attack or competition between IF-3 and aminoacyl-tRNA for the same ribosomal binding site. It was found that the 30S-aminoacyl-tRNA-codon complexes formed in the absence of IF-3 are intrinsically different from those prepared in the presence of IF-3. In the absence of IF-3, the ribosomal binding of aminoacyl-tRNA is a virtually irreversible process, since the bound aminoacyl-tRNA can neither be spontaneously released upon dilution nor exchanged for unbound aminoacyl-tRNA. In the presence of IF-3, the binding of one molecule of IF-3 per 30S ribosome renders the binding of aminoacyl-tRNA reversible upon dilution and promotes exchange between bound and unbound aminoacyl-tRNA. It is suggested that this difference is due to a conformational transition of the 30S ribosomal subunit induced by the binding of IF-3. The possible implications of this finding in relation to the mechanism of action of IF-3 and its functional role in the cell are discussed.

Keywords: ribosomes, conformation, protein synthesis, initiation, aminoacyl-tRNA binding

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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