title: The large ribosomal subunit protein L9 enables the growth of EF-P deficient cells and enhances small subunit maturation.
abstract: The loss of the large ribosomal protein L9 causes a reduction in translation fidelity by an unknown mechanism. To identify pathways affected by L9, we identified mutants of E. coli that require L9 for fitness. In a prior study, we characterized L9-dependent mutations in the essential GTPase Der (EngA). Here, we describe a second class of L9-dependent mutations that either compromise or inactivate elongation factor P (EF-P, eIF5A in eukaryotes). Without L9, Δefp cells are practically inviable. Cell fractionation studies revealed that, in both the Der and EF-P mutant cases, L9's activity reduces immature 16S rRNA in 30S particles and partially restores the abundance of monosomes. Inspired by these findings, we discovered that L9 also enhances 16S maturation in wild-type cells. Surprisingly, although the amount of immature 16S in 30S particles was found to be elevated in ΔrplI cells, the amount in polysomes was low and inversely correlated with the immature 16S abundance. These findings provide an explanation for the observed fitness increases afforded by L9 in these mutants and reveal particular physiological conditions in which L9 becomes critical. Additionally, L9 may affect the partitioning of small subunits containing immature 16S rRNA.
authors: The Burnett School of Biomedical Sciences, College of Medicine, The University of Central Florida, Orlando, FL, 32816, United States of America.
authors: Anusha
authors: A
authors: Naganathan
authors: Seattle Biomed, 307 Westlake Ave N, Suite 500, Seattle, WA, 98109, United States of America; Department of Global Health, University of Washington, 1510 N.E. San Juan Road, Seattle, WA, 98195, United States of America.
authors: Matthew P
authors: MP
authors: Wood
authors: The Burnett School of Biomedical Sciences, College of Medicine, The University of Central Florida, Orlando, FL, 32816, United States of America.
authors: Sean D
authors: SD
authors: Moore
mesh_terms: D009154:Mutation; D010445:Peptide Elongation Factors / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D012269:Ribosomal Proteins / Q000502:physiology*
chemical_list: D010445:Peptide Elongation Factors; D012336:RNA, Ribosomal, 16S; D012269:Ribosomal Proteins; C020746:factor EF-P; C049650:ribosomal protein L9