In vivo Characterization of the Type A and B Vancomycin-Resistant Enterococci (VRE) VanRS Two-Component Systems in Escherichia coli: A Nonpathogenic Model for Studying the VRE Signal Transduction Pathways

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 95; no. 20; pp. 11951 - 11956
• Main Authors: Silva, Jeffrey C., Haldimann, Andreas, Prahalad, Murali K., Walsh, Christopher T., Wanner, Barry L.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 29.09.1998; National Acad Sciences; National Academy of Sciences
• Subjects: Anti-Bacterial Agents - pharmacology; Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Base Sequence; Biochemistry; Biological Sciences; DNA Primers - genetics; Drug Resistance, Microbial - genetics; Enterococcus - drug effects; Enterococcus - genetics; Enterococcus - metabolism; Enterococcus faecalis - drug effects; Enterococcus faecalis - genetics; Enterococcus faecalis - metabolism; Enterococcus faecium - drug effects; Enterococcus faecium - genetics; Enterococcus faecium - metabolism; Enzymes; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - metabolism; Gene Expression; Genes; Genes, Bacterial; Genes, Reporter; Lac Operon; Microbiology; Models, Biological; Phosphatases; Phosphorylation; Physiological regulation; Plasmids; Polymerase Chain Reaction; Promoter Regions, Genetic; Protein Kinases - genetics; Protein Kinases - metabolism; Sensors; Signal Transduction; Transcription Factors - genetics; Transcription Factors - metabolism; Vancomycin - pharmacology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.20.11951

Escherichia coli reporter strains modeling the high-level type A and B vancomycin resistances of Enterococcus faecium BM4147 and Ent. faecalis have been developed to study the respective VanR-VanS two-component regulatory systems. PvanH-, PvanRa-, PvanY-, and PvanRb-lacZ fusions report on expression from the vancomycin-resistant enterococci promoters of the type A vanRSHAXYZ and type B vanRSYWHBX gene clusters. These strains also express from single-copy chromosomal genes vanRa, vanRb, or vanRSb behind their respective promoter (PvanRa or PvanRb) or vanSa or vanSb behind the rhamnose-inducible PrhaB. Results show that activation (phosphorylation) of the response regulator VanRa by its sensor kinase VanSa leads to transcriptional activation of both PvanH and PvanRa. Additionally, VanRb activates its cognate promoters PvanY and PvanRb, although this occurs only in the absence of VanSb and presumably is caused by VanRb phosphorylation by an unidentified endogenous E. coli kinase. Thus, VanSb interferes with activation of VanRb, probably by acting as a phospho-VanRb phosphatase. Although both VanRa and VanRb activate their cognate promoters, neither activates the heterologous PvanR, PvanH, or PvanY, arguing against the interchangeability of type A and B two-component regulatory switches in vancomycin-resistant enterococci. VanRa also is activated by the nonpartner kinase PhoR. Because this occurs in the absence of its inducing signal (Pi limitation), PhoR autophosphorylation apparently is regulated in vivo. Furthermore, the activation of VanRa caused by cross talk from PhoR in the absence of a signal allows distinction of cross talk from cross-regulation as the latter, but not the former, responds to environmental cues.