Figure 1.

Lmo1291 is a peptidoglycan O-acetyltransferase. A, Genetic organization of the L monocytogenes lmo1291 gene locus (in black) showing chromosomal coordinates (bp), putative terminators (black hairpins), and the flanking genes lmo1290 encoding a putative internalin (in white) and lmo1292 encoding a putative glycerophosphodiester phosphodiesterase (in gray). B, Map of putative domains of Lmo1291 (amino acid). C, Sequence alignment of O-acetyltransferases from Enterococcus faecalis (Efa), Lactococcus lactis (Lla), Staphylococcus aureus (Sau), and L. monocytogenes Lmo1291 (Lmo). Sequences were aligned using T-Coffee software. Amino acids in red are identical and residues in green are similar. Asterisks indicate the conserved catalytic triad of SGNH hydrolases. Efa, Lla, and Sau orthologs show 56%, 50%, and 55% identity to Lmo1291, respectively. D, Muropeptide profile of the highly purified cell walls of EGDe and its isogenic ΔoatA mutant. Peaks highlighted by an asterisk indicate muropeptides absent from the ΔoatA mutant. Major peaks were analyzed by MALDI MS/MS and their respective structure are indicated above the corresponding peak. Deacetylated muropeptides are indicated in red. Muropeptides that are O-acetylated are highlighted by the addition of the OAc moiety in blue. Dotted arrows indicate the relationship between the different O-acetylated muropeptides and their parent muropeptides that lack the OAc moiety. E, Localization of PGN modifications by OatA (O-acetylation in blue) and PgdA (N-deacetylation in red). MALDI indicates matrix-assisted laser desorption ionization; MS/MS, tandem mass spectrometry.