Identification of Mur, an atypical peptidoglycan hydrolase derived from Leuconostoc citreum

A gene encoding a protein homologous to known bacterial N-acetyl-muramidase s has been cloned from Leuconostoc citreum by a PCR-based approach. The enc oded protein, Mur, consists of 209 amino acid residues with a calculated mo lecular mass of 23,821 Da including a 31-amino-acid putative Signal peptide . In contrast to most of the other known peptidoglycan hydrolases, L. citre um Mur protein does not contain amino acid repeats involved in cell wall bi nding. The purified L. citreum Mur protein was shown to exhibit peptidoglyc an-hydrolyzing activity by renaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An active chimeric protein was constructed by fusion oft. citreum Mur to the C-terminal repeat-containing domain (cA) of AcmA, t he major autolysin of Lactococcus lactis. Expression of the Mur-cA fusion p rotein was able to complement an acmA mutation in L. lactis; normal cell se paration after cell division was restored by Mur-cA expression.