title: The Cpx envelope stress response modifies peptidoglycan cross-linking via the L,D-transpeptidase LdtD and the novel protein YgaU.
abstract: The Cpx envelope stress response mediates a complex adaptation to conditions that cause protein misfolding in the periplasm. A recent microarray study demonstrated that Cpx response activation led to changes in the expression of genes known, or predicted, to be involved in cell wall remodeling. We sought to characterize the changes that the cell wall undergoes during activation of the Cpx pathway in Escherichia coli. Luminescent reporters of gene expression confirmed that LdtD, a putative l,d-transpeptidase; YgaU, a protein of unknown function; and Slt, a lytic transglycosylase, are upregulated in response to Cpx-inducing conditions. Phosphorylated CpxR binds to the upstream regions of these genes, which contain putative CpxR binding sites, suggesting that regulation is direct. We show that the activation of the Cpx response causes an increase in the abundance of diaminopimelic acid (DAP)-DAP cross-links that involves LdtD and YgaU. Altogether, our data indicate that changes in peptidoglycan structure are part of the Cpx-mediated adaptation to envelope stress and indicate a role for the uncharacterized gene ygaU in regulating cross-linking.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.
authors.forename: Margarita
authors.initials: M
authors.lastname: Bernal-Cabas
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Agencia Estatal Consejo Superior de Investigaciones Científicas (CSIC-UAM), Campus de Cantoblanco, Madrid, Spain.
authors.forename: Juan Alfonso
authors.initials: JA
authors.lastname: Ayala
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada traivio@ualberta.ca.
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Raivio
mesh_terms: D019881:Aminoacyltransferases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002473:Cell Wall / Q000737:chemistry; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006026:Glycoside Hydrolases / Q000378:metabolism*; D010457:Peptidoglycan / Q000032:analysis; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D013312:Stress, Physiological
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D010457:Peptidoglycan; C000595833:YgaU protein, E coli; C085504:CpxR protein, Bacteria; D019881:Aminoacyltransferases; C022330:peptidoglycan transpeptidase; D006026:Glycoside Hydrolases; C085428:slt protein, E coli