TY - JOUR TI - Factors essential for L,D-transpeptidase-mediated peptidoglycan cross-linking and β-lactam resistance in Escherichia coli AU - Hugonnet, Jean-Emmanuel AU - Mengin-Lecreulx, Dominique AU - Monton, Alejandro AU - den Blaauwen, Tanneke AU - Carbonnelle, Etienne AU - Veckerlé, Carole AU - Brun, Yves, V. AU - van Nieuwenhze, Michael AU - Bouchier, Christiane AU - Tu, Kuyek AU - Rice, Louis B AU - Arthur, Michel A2 - Gilmore, Michael S VL - 5 PY - 2016 DA - 2016/10/21 SP - e19469 C1 - eLife 2016;5:e19469 DO - 10.7554/eLife.19469 UR - https://doi.org/10.7554/eLife.19469 AB - The target of β-lactam antibiotics is the D,D-transpeptidase activity of penicillin-binding proteins (PBPs) for synthesis of 4→3 cross-links in the peptidoglycan of bacterial cell walls. Unusual 3→3 cross-links formed by L,D-transpeptidases were first detected in Escherichia coli more than four decades ago, however no phenotype has previously been associated with their synthesis. Here we show that production of the L,D-transpeptidase YcbB in combination with elevated synthesis of the (p)ppGpp alarmone by RelA lead to full bypass of the D,D-transpeptidase activity of PBPs and to broad-spectrum β-lactam resistance. Production of YcbB was therefore sufficient to switch the role of (p)ppGpp from antibiotic tolerance to high-level β-lactam resistance. This observation identifies a new mode of peptidoglycan polymerization in E. coli that relies on an unexpectedly small number of enzyme activities comprising the glycosyltransferase activity of class A PBP1b and the D,D-carboxypeptidase activity of DacA in addition to the L,D-transpeptidase activity of YcbB. KW - β-lactam KW - PBP1b KW - PBP5 KW - L,D-transpeptidase KW - mecillinam KW - (p)ppGpp JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -