 Bacterial initiation factor IF2

Bacterial initiation factor IF2 is a GTPase and bacterial translation initiation factor that helps recruit and position the initiator transfer RNA in bacterial biological translation. Its C-terminal region recognizes the attached formylmethionine. GTP binding and GTP hydrolysis participate in the transition toward a complete elongation-competent ribosome.^[ref]

The relevant objects are distinct: bacterial initiation factor IF2 is a protein, GTP is a bound nucleotide, and formylmethionine is carried by transfer RNA. Recognizing the attached amino acid is not the same reaction as charging the transfer RNA.

In an original assay design, compare initiator-tRNA binding to a 30S initiation complex with a later measurement of peptide bond formation after adding the large ribosomal subunit. A preparation could bind the carrier successfully yet fail at a subsequent rearrangement. The two readouts therefore test different stages, rather than two interchangeable measures of IF2 activity.