Genetic analysis of translation initiation in bacteria: An initiator tRNA‐centric view

Abstract

AbstractTranslation of messenger RNA (mRNA) in bacteria occurs in the steps of initiation, elongation, termination, and ribosome recycling. The initiation step comprises multiple stages and uses a special transfer RNA (tRNA) called initiator tRNA (i‐tRNA), which is first aminoacylated and then formylated using methionine and N10‐formyl‐tetrahydrofolate (N10‐fTHF), respectively. Both methionine and N10‐fTHF are produced via one‐carbon metabolism, linking translation initiation with active cellular metabolism. The fidelity of i‐tRNA binding to the ribosomal peptidyl‐site (P‐site) is attributed to the structural features in its acceptor stem, and the highly conserved three consecutive G‐C base pairs (3GC pairs) in the anticodon stem. The acceptor stem region is important in formylation of the amino acid attached to i‐tRNA and in its initial binding to the P‐site. And, the 3GC pairs are crucial in transiting the i‐tRNA through various stages of initiation. We utilized the feature of 3GC pairs to investigate the nuanced layers of scrutiny that ensure fidelity of translation initiation through i‐tRNA abundance and its interactions with the components of the translation apparatus. We discuss the importance of i‐tRNA in the final stages of ribosome maturation, as also the roles of the Shine–Dalgarno sequence, ribosome heterogeneity, initiation factors, ribosome recycling factor, and coevolution of the translation apparatus in orchestrating a delicate balance between the fidelity of initiation and/or its leakiness to generate proteome plasticity in cells to confer growth fitness advantages in response to the dynamic nutritional states.