Phylogenetic Analysis of L4-Mediated Autogenous Control of the S10 Ribosomal Protein Operon

Abstract

ABSTRACT We investigated the regulation of the S10 ribosomal protein (r-protein) operon among members of the gamma subdivision of the proteobacteria, which includes Escherichia coli . In E. coli , this 11-gene operon is autogenously controlled by r-protein L4. This regulation requires specific determinants within the untranslated leader of the mRNA. Secondary structure analysis of the S10 leaders of five enterobacteria ( Salmonella typhimurium , Citrobacter freundii , Yersinia enterocolitica , Serratia marcescens , and Morganella morganii ) and two nonenteric members of the gamma subdivision ( Haemophilus influenzae and Vibrio cholerae ) shows that these foreign leaders share significant structural homology with the E. coli leader, particularly in the region which is critical for L4-mediated autogenous control in E. coli . Moreover, these heterologous leaders produce a regulatory response to L4 oversynthesis in E. coli . Our results suggest that an E. coli -like L4-mediated regulatory mechanism may operate in all of these species. However, the mechanism is not universally conserved among the gamma subdivision members, since at least one, Pseudomonas aeruginosa , does not contain the required S10 leader features, and its leader cannot provide the signals for regulation by L4 in E. coli . We speculate that L4-mediated autogenous control developed during the evolution of the gamma branch of proteobacteria.