The occurrence of duplicate lysyl-tRNA synthetase gene homologs in Escherichia coli and other procaryotes

Abstract

The lysyl-tRNA synthetase (LysRS) system of Escherichia coli K-12 consists of two genes, lysS, which is constitutive, and lysU, which is inducible. It is of importance to know how extensively the two-gene LysRS system is distributed in procaryotes, in particular, among members of the family Enterobacteriaceae. To this end, the enterics E. coli K-12 and B; E. coli reference collection (ECOR) isolates EC2, EC49, EC65, and EC68; Shigella flexneri; Salmonella typhimurium; Klebsiella pneumoniae; Enterobacter aerogenes; Serratia marcescens; and Proteus vulgaris and the nonenterics Pseudomonas aeruginosa and Bacillus megaterium were grown in AC broth to a pH of 5.5 or less or cultured in SABO medium at pH 5.0. These growth conditions are known to induce LysRS activity (LysU synthesis) in E. coli K-12. Significant induction of LysRS activity (twofold or better) was observed in the E. coli strains, the ECOR isolates, S. flexneri, K. pneumoniae, and E. aerogenes. To demonstrate an association between LysRS induction and two distinct LysRS genes, Southern blotting was performed with a probe representing an 871-bp fragment amplified from an internal portion of the coding region of the lysU gene. In initial experiments, chromosomal DNA from E. coli K-12 strain MC4100 (lysS ؉ lysU ؉ ) was double digested with either BamHI and HindIII or BamHI and SalI, producing hybridizable fragments of 12.4 and 4.2 kb and 6.6 and 5.2 kb, respectively. Subjecting the chromosomal DNA of E. coli K-12 strain GNB10181 (lysS ؉ ⌬lysU) to the same regimen established that the larger fragment from each digestion contained the lysU gene. The results of Southern blot analysis of the other bacterial strains revealed that two hybridizable fragments were obtained from all of the E. coli and ECOR collection strains examined and S. flexneri, K. pneumoniae, and E. aerogenes. Only one lysU homolog was found with S. typhimurium and S. marcescens, and none was obtained with P. vulgaris. A single hybridizable band was found with both P. aeruginosa and B. megaterium. These results show that the dual-gene LysRS system is not confined to E. coli K-12 and indicate that it may have first appeared in the genus Enterobacter.

Molecular and Functional Characterization of Salmonella enterica Serovar Typhimurium poxA Gene: Effect on Attenuation of Virulence and Protection

“…It appears then that E. coli encodes three lysyl-tRNA synthetases, LysS, LysU, and GenX. Although the lysS gene has been mapped at 66.2 min on the Salmonella chromosome, a location similar to that of the E. coli counterpart (12), the lysU gene is absent from the Salmonella genome (39). To our knowledge, this is the first report showing that PoxA is the second putative lysyl-tRNA synthetase in Salmonella (the first being LysS) and that genX and poxA are allelic.…”

Human Immunodeficiency Virus Type 1 (HIV-1) Viral Protein R (Vpr) Interacts with Lys-tRNA Synthetase: Implications for Priming of HIV-1 Reverse Transcription

“…This result is in keeping with that of Martinez and Mirande (49), who found that the N-terminal extension (amino acids 1 to 69) of S. cerevisiae LysRS was dispensable in vivo for aminoacylation activities. Furthermore, structural data from the E. coli LysRS S protein indicated that deletion of the N-terminal 30 amino acids (corresponding to amino acids 64 to 93 of human LysRS by sequence comparison) did not affect the ability of the protein to specifically recognize the anticodon loop of tRNA Lys and catalyze aminoacylation (9,58). Several highly conserved residues that are thought to be involved in binding to Mg 2ϩ and ATP have been identified in class II aminoacyl synthetases (to which LysRS belongs) (20).…”

Expression of DuplicatemsaGenes in the Salmonid PathogenRenibacteriumsalmoninarum

“…Gene duplication is a way to amplify production of a gene product or to ensure the synthesis of an essential, multifunctional protein. Expression of both msa1 and msa2 may be (21,37). While both copies of msa have identical sequences up to 40 bp upstream of the ORF, the sequences beyond are quite divergent.…”