ABSTRACT
The Escherichia coli protein YjeQ is a circularly permuted GTPase that is broadly conserved in bacteria. An emerging body of evidence, including cofractionation and in vitro binding to the ribosome, altered polysome profiles after YjeQ depletion, and stimulation of GTPase activity by ribosomes, suggests that YjeQ is involved in ribosome function. The growth of strains lacking YjeQ in culture is severely compromised. Here, we probed the cellular function of YjeQ with genetic screens of ordered E. coli genomic libraries for suppressors and enhancers of the slow-growth phenotype of a ΔyjeQ strain. Screening for suppressors using an ordered library of 374 clones overexpressing essential genes and genes associated with ribosome function revealed that two GTPases, Era and initiation factor 2, ameliorated the growth and polysome defects of the ΔyjeQ strain. In addition, seven bona fide enhancers of slow growth were identified (Δtgt, ΔksgA, ΔssrA, ΔrimM, ΔrluD, ΔtrmE/mnmE, and ΔtrmU/mnmA) among 39 deletions (in genes associated with ribosome function) that we constructed in the ΔyjeQ genetic background. Taken in context, our work is most consistent with the hypothesis that YjeQ has a role in late 30S subunit biogenesis.
Function of initiation factor 1 in the binding and release of initiation factor 2 from ribosomal initiation complexes in Escherichia coli.
