Affiliation:
1. Department of Microbiology and Immunology, Emory University, Atlanta, Georgia 30322.
Abstract
We isolated spontaneous mutations (pmrA) in the smooth strain Salmonella typhimurium LT2 that show increased resistance to the cationic antibacterial proteins of human neutrophils and to the drug polymyxin B. The mutation in one strain, JKS5, maps to 93 min on the S. typhimurium chromosome, near the proP gene and the melAB operon. The mutation, designated pmrA505, confers a 1,000-fold increase in resistance to polymyxin B and a 2- to 4-fold increase in resistance to neutrophil proteins. We cloned both the pmrA505 and pmrA+ alleles and found that the pmrA+ gene is partially dominant over pmrA505. DNA sequence analysis of the pmrA505 clone revealed three open reading frames (ORFs). The deduced amino acid sequences indicated that ORF1 encodes a 548-amino-acid (aa) protein with a putative membrane-spanning domain and no significant homology to any known protein. ORF2 and ORF3, which encode 222- and 356-aa proteins, respectively, show strong homology with the OmpR-EnvZ family of two-component regulatory systems. ORF2 showed homology with a number of response regulators, including OmpR and PhoP, while ORF3 showed homology to histidine kinase-sensor proteins EnvZ and PhoR. Genetic analysis of the cloned genes suggested that ORF2 contained the pmrA505 mutation. Comparison of the pmrA505 and pmrA+ ORF2 DNA sequences revealed a single G-A transition, which would result in a His-to-Arg substitution at position 81 in the ORF2 mutant protein. We therefore designate ORF2 PmrA and ORF3 PmrB. The function of ORF1 is unknown.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference56 articles.
1. Basic local alignment search tool;Altschul S. F.;J. Mol. Biol.,1990
2. The VanSVanR two-component regulatory system controls synthesis of depsipeptide peptidoglycan precursors in Enterococcusfaecium BM4147;Arthur M.;J. Bacteriol.,1992
3. Ausubel F. M. R. Brent R. E. Kingston D. D. Moore J. G. Seidman J. A. Smith and K. Struhl. 1991. Current protocols in molecular biology vol. 1 and 2. Greene Publishing Associates & Wiley Interscience New York.
4. Rapid mapping in Salmonella typhimurium with Mud-P22 prophages;Benson N. R.;J. Bacteriol.,1992
5. Positive selection for loss of tetracycline resistance;Bochner B. R.;J. Bacteriol.,1980
Cited by
164 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献