Open AccessLactococcus lactis Gene yjgB Encodes a γ- d -Glutaminyl- l -Lysyl- Endopeptidase Which Hydrolyzes Peptidoglycan
Author(s) -
Yulia Redko,
Pascal Courtin,
Christine Mézange,
Carine Huard,
MariePierre ChapotChartier
Publication year - 2007
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.00705-07
Subject(s) - peptidoglycan , lactococcus lactis , endopeptidase , biochemistry , tripeptide , chemistry , peptide , cell wall , biology , enzyme , bacteria , lactic acid , genetics
YjgB is one of five peptidoglycan hydrolases previously identified inLactococcus lactis . Analysis of its amino acid sequence revealed that YjgB contains an NlpC/P60 domain, whereas no specific cell wall binding domain or motif could be identified. The NlpC/P60 family is characterized by three conserved residues, a cysteine, a histidine, and a polar residue. In agreement with the presence of a Cys residue in the catalytic site of YjgB, its enzymatic activity was enhanced in the presence of dithiothreitol. Peptidoglycan-hydrolyzing activity of YjgB was detected in growing cells of anL. lactis strain overexpressing YjgB, as revealed by the presence of disaccharide (DS)-dipeptide in the muropeptide composition of the overexpressing strain. YjgB hydrolyzes the peptide chains ofL. lactis muropeptides between γ-d -Gln andl -Lys residues. Its hydrolytic activity was detected on DSs with tetra- and pentapeptide chains, whereas hydrolytic activity was very low on DS-tripeptides. Thus, we demonstrated that YjgB is an endopeptidase which cleaves γ-d -Gln-l -Lys bonds in peptide chains ofL. lactis peptidoglycan.