title: The CHAP domain of Cse functions as an endopeptidase that acts at mature septa to promote Streptococcus thermophilus cell separation.
abstract: Cell separation is dependent on cell wall hydrolases that cleave the peptidoglycan shared between daughter cells. In Streptococcus thermophilus, this step is performed by the Cse protein whose depletion resulted in the formation of extremely long chains of cells. Cse, a natural chimeric enzyme created by domain shuffling, carries at least two important domains for its activity: the LysM expected to be responsible for the cell wall-binding and the CHAP domain predicted to contain the active centre. Accordingly, the localization of Cse on S. thermophilus cell surface has been undertaken by immunogold electron and immunofluorescence microscopies using of antibodies raised against the N-terminal end of this protein. Immunolocalization shows the presence of the Cse protein at mature septa. Moreover, the CHAP domain of Cse exhibits a cell wall lytic activity in zymograms performed with cell walls of Micrococcus lysodeikticus, Bacillus subtilis and S. thermophilus. Additionally, RP-HPLC analysis of muropeptides released from B. subtilis and S. thermophilus cell wall after digestion with the CHAP domain shows that Cse is an endopeptidase. Altogether, these results suggest that Cse is a cell wall hydrolase involved in daughter cell separation of S. thermophilus.
authors.affiliation: Laboratoire de Génétique et Microbiologie, UMR INRA/UHP 1128, IFR 110, Nancy-Université, BP 239, 54506 Vandoeuvre-lès-Nancy, France.
authors.forename: Séverine
authors.initials: S
authors.lastname: Layec
authors.forename: Joëlle
authors.initials: J
authors.lastname: Gérard
authors.forename: Valérie
authors.initials: V
authors.lastname: Legué
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Chapot-Chartier
authors.forename: Pascal
authors.initials: P
authors.lastname: Courtin
authors.forename: Frédéric
authors.initials: F
authors.lastname: Borges
authors.forename: Bernard
authors.initials: B
authors.lastname: Decaris
authors.forename: Nathalie
authors.initials: N
authors.lastname: Leblond-Bourget
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D002473:Cell Wall / Q000201:enzymology; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D009154:Mutation; D054730:Protein Interaction Domains and Motifs; D012329:RNA, Bacterial / Q000235:genetics; D048249:Streptococcus thermophilus / Q000166:cytology / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D010450:Endopeptidases