TAILIEUCHUNG - Báo cáo khoa học: AcmA of Lactococcus lactis is an N-acetylglucosaminidase with an optimal number of LysM domains for proper functioning

AcmA, the major autolysin ofLactococcus lactisMG1363 is a modular protein consisting of an N-terminal active site domain and a C-terminal peptidoglycan-binding domain. The active site domain is homologous to that of muramidase-2 of Enterococcus hirae, however, RP-HPLC analysis of muropeptides released fromBacillus subtilispeptidoglycan, after diges-tion with AcmA, shows that AcmA is an N-acetylglucosaminidase. | iFEBS Journal AcmA of Lactococcus lactis is an N-acetylglucosaminidase with an optimal number of LysM domains for proper functioning Anton Steen1 Girbe Buist1 Gavin J. Horsburgh2 Gerard Venema1 Oscar P. Kuipers1 Simon J. Foster2 and Jan Kok1 1 Department of Genetics Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen the Netherlands 2 Department of Molecular Biology and Biotechnology University of Sheffield UK Keywords autolysin AcmA Lactococcus lactis LysM domain N-acetylglucosaminidase Correspondence G. Buist Department of Genetics Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen Kerklaan 30 9751 NN Haren the Netherlands Fax 31 50 3632348 Tel 31 50 3632287 E-mail Note A. Steen and G. Buist contributed equally to this study Received 23 December 2004 revised 23 March 2005 accepted 6 April 2005 doi AcmA the major autolysin of Lactococcus lactis MG1363 is a modular protein consisting of an N-terminal active site domain and a C-terminal peptidoglycan-binding domain. The active site domain is homologous to that of muramidase-2 of Enterococcus hirae however RP-HPLC analysis of muropeptides released from Bacillus subtilis peptidoglycan after digestion with AcmA shows that AcmA is an N-acetylglucosaminidase. In the C-terminus of AcmA three highly similar repeated regions of 45 amino acid residues are present which are separated by short nonhomologous sequences. The repeats of AcmA which belong to the lysine motif LysM domain family were consecutively deleted removed or alternatively one additional repeat was added without destroying the cell wall-hydrolyzing activity of the enzyme in vitro although AcmA activity was reduced in all cases. In vivo proteins containing no or only one repeat did not give rise to autolysis of lactococcal cells whereas separation of the producer cells from the chains was incomplete. Exogenously added AcmA deletion derivatives .

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