Remodeling of Crossbridges Controls Peptidoglycan Crosslinking Levels in Bacterial Cell Walls

Abstract

Cell walls are barriers found in almost all known bacterial cells. These structures establish a controlled interface between the external environment and vital cellular components. A primary component of cell wall is a highly crosslinked matrix called peptidoglycan (PG). PG crosslinking, carried out by transglycosylases and transpeptidases, is necessary for proper cell wall assembly. Transpeptidases, targets of {beta}-lactam antibiotics, stitch together two neighboring PG stem peptides (acyl-donor and acyl-acceptor strands). We recently described a novel class of cellular PG probes that were processed exclusively as acyl-donor strands. Herein, we have accessed the other half of the transpeptidase reaction by developing probes that are processed exclusively as acyl-acceptor strands. The critical nature of the crossbridge on the PG peptide was demonstrated in live bacterial cells and surprising promiscuity in crossbridge primary sequence was found in various bacterial species. Additionally, acyl-acceptor probes provided insight into how chemical remodeling of the PG crossbridge (e.g., amidation) can modulate crosslinking levels, thus establishing a physiological role of PG structural variations. Together, the acyl-donor and -acceptor probes will provide a versatile platform to interrogate PG crosslinking in physiologically relevant settings. SYNOPSIS TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/840405v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@199b09dorg.highwire.dtl.DTLVardef@11a2193org.highwire.dtl.DTLVardef@923d89org.highwire.dtl.DTLVardef@106108a_HPS_FORMAT_FIGEXP M_FIG C_FIG