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Claes, IJ, Schoofs, G, Regulski, K, Courtin, P, Chapot-Chartier, MP, Rolain, T, Hols, P, von Ossowski, I, Reunanen, J, de Vos, WM, Palva, A, Vanderleyden, J, De Keersmaecker, SC and Lebeer, S (2012) Genetic and biochemical characterization of the cell wall hydrolase activity of the major secreted protein of Lactobacillus rhamnosus GG. PLoS ONE 7:e31588


Lactobacillus rhamnosus GG (LGG) produces two major secreted proteins, designated here Msp1 (LGG_00324 or p75) and Msp2 (LGG_00031 or p40), which have been reported to promote the survival and growth of intestinal epithelial cells. Intriguingly, although each of these proteins shares homology with cell wall hydrolases, a physiological function that correlates with such an enzymatic activity remained to be substantiated in LGG. To investigate the bacterial function, we constructed knock-out mutants in the corresponding genes aiming to establish a genotype to phenotype relation. Microscopic examination of the msp1 mutant showed the presence of rather long and overly extended cell chains, which suggests that normal daughter cell separation is hampered. Subsequent observation of the LGG wild-type cells by immunofluorescence microscopy revealed that the Msp1 protein accumulates at the septum of exponential-phase cells. The cell wall hydrolyzing activity of the Msp1 protein was confirmed by zymogram analysis. Subsequent analysis by RP-HPLC and mass spectrometry of the digestion products of LGG peptidoglycan (PG) by Msp1 indicated that the Msp1 protein has D-glutamyl-L-lysyl endopeptidase activity. Immunofluorescence microscopy and the failure to construct a knock-out mutant suggest an indispensable role for Msp2 in priming septum formation in LGG.


PubMed PMC3281093 Online version:10.1371/journal.pone.0031588


Bacterial Proteins/metabolism; Cell Wall/enzymology; Endopeptidases; Hydrolases/genetics; Hydrolases/metabolism; Lactobacillus rhamnosus/enzymology; Mutant Proteins; Peptidoglycan/metabolism



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:0004175: endopeptidase activity

IMP: Inferred from Mutant Phenotype:


IMP based on evidence showed on Fig. 2. Phase-contrast (A,B&C) and Transmission Electron Microscopy (TEM) pictures (D&E) of LGG wild-type (A&D), msp1 mutant cells CMPG10200 (B&E) and plasmid-complemented CMPG10203 cells (C). The msp1 knock-out mutant shows a defect in cell separation as visualized by phase contrast and electron microscopy. Plasmid-mediated complementation of the mutant restored the wild-type phenotype.

CACAO 4124

See also


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