Enzymes carrying NlpC/p60 domains, for instance RipA and RipB from Mycobacterium tuberculosis, are bacterial peptidoglycan hydrolases cleaving the peptide stems and contribute to cell wall remodeling during cell division. A member of this protein family, RipD (Rv1566c) from M. tuberculosis described here, displays sequence alterations in the NlpC/p60 catalytic triad and carries a pentapeptide repeat at its carboxy-terminus. Bioinformatics analysis revealed RipD-like proteins in eleven mycobacterial genomes, while similar pentapeptide-repeats occur in cell wall-localized bacterial proteins and in a mycobacteriophage. In contrast to previously known members of the NlpC/p60 family, RipD does not show peptidoglycan... More
Enzymes carrying NlpC/p60 domains, for instance RipA and RipB from Mycobacterium tuberculosis, are bacterial peptidoglycan hydrolases cleaving the peptide stems and contribute to cell wall remodeling during cell division. A member of this protein family, RipD (Rv1566c) from M. tuberculosis described here, displays sequence alterations in the NlpC/p60 catalytic triad and carries a pentapeptide repeat at its carboxy-terminus. Bioinformatics analysis revealed RipD-like proteins in eleven mycobacterial genomes, while similar pentapeptide-repeats occur in cell wall-localized bacterial proteins and in a mycobacteriophage. In contrast to previously known members of the NlpC/p60 family, RipD does not show peptidoglycan hydrolase activity, which is consistent with the sequence alterations at the catalytic site. A strong interaction of the catalytically inactive core domain with peptidoglycan is however retained, presenting the first example of the NlpC/p60 domains that evolved to a non-catalytic peptidoglycan binding function. Full-length RipD, carrying the C-terminal repeat, shows however a decrease in binding affinity to peptidoglycan, suggesting that the C-terminal tail modulates the interaction with bacterial call wall components. The pentapeptide repeat at the carboxy-terminus does not adopt a defined secondary structure in solution which is in accordance with results from the 1.17Å crystal structure of the protein carrying two repeat units.