The Cell Wall Hydrolytic NlpC/P60 Endopeptidases in Mycobacterial Cytokinesis: A Structural Perspective

Abstract

In preparation for division, bacteria replicate their DNA and segregate the newly formed chromosomes. A division septum then assembles between the chromosomes, and the mother cell splits into two identical daughters due to septum degradation. A major constituent of bacterial septa and of the whole cell wall is peptidoglycan (PGN), an essential cell wall polymer, formed by glycan chains of β−(1-4)-linked-N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc), cross-linked by short peptide stems. Depending on the amino acid located at the third position of the peptide stem, PGN is classified as either Lys-type or meso-diaminopimelic acid (DAP)-type. Hydrolytic enzymes play a crucial role in the degradation of bacterial septa to split the cell wall material shared by adjacent daughter cells to promote their separation. In mycobacteria, a key PGN hydrolase, belonging to the NlpC/P60 endopeptidase family and denoted as RipA, is responsible for the degradation of septa, as the deletion of the gene encoding for this enzyme generates abnormal bacteria with multiple septa. This review provides an update of structural and functional data highlighting the central role of RipA in mycobacterial cytokinesis and the fine regulation of its catalytic activity, which involves multiple molecular partners.

Enterococcus NlpC/p60 Peptidoglycan Hydrolase SagA Localizes to Sites of Cell Division and Requires Only a Catalytic Dyad for Protease Activity

“…For instance, unlike SagA-NlpC/p60, the RipA NlpC/p60 domain has a prominent loop occluding its entire binding groove (Figure S9A). This loop is a putative inhibitory prodomain that is proposed to be proteolytically cleaved in vivo for activation of RipA at the Mycobacterium tuberculosis septum. − The Staphylococcus aureus CwlT NlpC/p60 domain, on the contrary, shows a loop protruding from its bottom ridge partially blocking the groove near the site of Tyr493 in SagA-NlpC/p60, but it also has a flatter and more open groove periphery (Figure S9B). The E. coli Spr NlpC/p60 domain contains a similar loop, but it actually points into the groove, as do several bulky residues at the periphery (Figure S9C).…”

Prolonged Heat Stress of Lactobacillus paracasei GCRL163 Improves Binding to Human Colorectal Adenocarcinoma HT-29 Cells and Modulates the Relative Abundance of Secreted and Cell Surface-Located Proteins

“…123 Models for activating peptidoglycan hydrolysis by CwlO-NlpC/p60 proteins include conformational changes though interaction with the FtsE/X, 126,127 formation of multimers which bring the catalytic sites together to achieve an active complex, 127 and proteolytic release of the catalytic region. 128 Our proteomic data indicated significantly higher abundance of FtsE and FtsX in CFE fractions at supra-optimal temperatures and FtsE in TS fractions at 45 °C concomitantly with higher abundance of the, but not the surface antigen-CwlO protein, despite the relatively lower growth rate at this temperature, hence suggesting that Msp2 was not necessarily only coupled with rapid cell division. Whether these redundant proteins are differentially responsible for septation and autolysis and interact similarly or differentially with the FtsE/X complex and other protein cofactors to achieve peptidoglycan hydrolysis following a stress signal remains to be explored.…”

“…coli, although there is less understanding about the complexities of the autolysin control in Gram-positive species . Models for activating peptidoglycan hydrolysis by CwlO-NlpC/p60 proteins include conformational changes though interaction with the FtsE/X, , formation of multimers which bring the catalytic sites together to achieve an active complex, and proteolytic release of the catalytic region . Our proteomic data indicated significantly higher abundance of FtsE and FtsX in CFE fractions at supra-optimal temperatures and FtsE in TS fractions at 45 °C concomitantly with higher abundance of the, but not the surface antigen-CwlO protein, despite the relatively lower growth rate at this temperature, hence suggesting that Msp2 was not necessarily only coupled with rapid cell division.…”

MagC is a NplC/P60‐like member of the α‐2‐macroglobulin Mag complex of Pseudomonas aeruginosa that interacts with peptidoglycan

“…6) [48]. It is interesting to note that in a similar manner, the NlpC/P60 protein RipA from M. tuberculosis, which has a D,L‐endopeptidase activity also shows a direct interaction of its conserved Asp382 with a modelled γ‐D‐Glu moiety [52,53].…”