Initiation factor 2-dependent ribosomal binding of N-formylmethionyl-transfer RNA without added guanosine triphosphate.

Evidence is presented that suggests that GTP (or 5'-guanylylmethylene diphosphonate) is not essential for either formation of an AUG-directed, initiation factor IF-2-dependent initiation complex on the 30S subunit or for positioning of fMet-tRNA on the peptidyl site. However, recycling of limiting amounts of IF-2 requires both GTP and the 50S subunit. The formation of the complex IF-2-30S as an intermediate in polypeptidechain initiation is suggested.