Cleavage of Braun’s lipoprotein Lpp from the bacterial peptidoglycan by a paralog of l , d -transpeptidases, LdtF

Significance Bacterial cell walls contain a protective exoskeleton, peptidoglycan, which is a target of several clinically important antimicrobials. In gram-negative bacteria, peptidoglycan is covered by an additional lipid layer, outer membrane, that serves as a permeability barrier against the entry of toxic molecules. In some bacteria, an abundant lipoprotein, Lpp, staples the outer membrane to peptidoglycan to maintain the structural integrity of the cell envelope. In this study, we identify a previously unknown hydrolytic enzyme that cleaves Lpp from the peptidoglycan and show how the outer membrane–peptidoglycan linkages are modulated in Escherichia coli . Overall, this study helps in understanding the fundamental bacterial cell wall biology and in the identification of alternate drug targets for the development of new antimicrobials.