Bacterial translation initiation

A reusable bacterial module for assembly of a translation-competent 70S initiation complex. IF2 and IF3 associate with the 30S subunit early, IF1 stabilizes their binding and organizes the preinitiation complex, and IF2 promotes initiator fMet-tRNA accommodation and 50S joining while hydrolyzing GTP. The boundary ends with factor release and formation of the mature 70S initiation complex. Ribosome biogenesis, initiator-tRNA aminoacylation and formylation, elongation, and termination are excluded. RRF/EF-G-driven recycling is outside the module, but IF3 stabilization of newly split 30S subunits is retained as the recycling-to-initiation interface.

The module is bacteria-scoped and uses Pseudomonas putida KT2440 and Escherichia coli K-12 proteins as concrete leaf exemplars. IF2 appears in both the early 30S-loading part and the terminal subunit-joining part because the same factor spans both phases; this is not a duplicated pathway requirement. The first PRECEDES edge represents the kinetically favored Escherichia coli route measured in PMID:22562136, not an obligatory universal factor-binding sequence; factor occupancy overlaps and mRNA can bind at different times. The PANTHER selectors are pan-taxonomic families containing bacterial, organellar, and cytosolic homologs. Their official labels are retained verbatim even where they are organelle-oriented. The explicit bacterial taxon context and exact bacterial UniProt exemplars constrain their use here without claiming that the family identifiers themselves are bacteria-specific.