Characterization of<i>Helicobacter pylori</i>Lytic Transglycosylases Slt and MltD

Chaput, Catherine; Labigne, Agnès; Boneca, Ivo Gomperts

doi:10.1128/jb.01270-06

Cited by 48 publications

(53 citation statements)

References 24 publications

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“…The functions of LtgB and LtgE remain a mystery (19), although mutation of ltgE has a slight effect on PG dimer release (Fig. 2), a result consistent with its possible role as an endolytic transglycosylase as predicted from H. pylori studies (2).…”

Section: Discussionsupporting

confidence: 62%

“…A putative lytic transglycosylase gene (ltgE) encoding a protein similar to E. coli MltD was identified in the gonococcal chromosome by sequence comparisons (Table 2). An analysis of H. pylori mutants deficient in the LtgE homologue (MltD) indicated that the H. pylori enzyme acts as an endo-type lytic transglycosylase, shortening chain length and increasing anhydro ends in intact cell walls (2). Such an activity might generate more substrates for exo-type lytic transglycosylases and increase anhydro PG monomer production.…”

Section: Resultsmentioning

confidence: 99%

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Neisseria gonorrhoeae Uses Two Lytic Transglycosylases To Produce Cytotoxic Peptidoglycan Monomers

et al. 2008

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Peptidoglycan fragments released by Neisseria gonorrhoeae contribute to the inflammation and ciliated cell death associated with gonorrhea and pelvic inflammatory disease. However, little is known about the production and release of these fragments during bacterial growth. Previous studies demonstrated that one lytic transglycosylase, LtgA, was responsible for the production of approximately half of the released peptidoglycan monomers. Systematic mutational analysis of other putative lytic transglycosylase genes identified lytic transglycosylase D (LtgD) as responsible for release of peptidoglycan monomers from gonococci. An ltgA ltgD double mutant was found not to release peptidoglycan monomers and instead released large, soluble peptidoglycan fragments. In pulse-chase experiments, recycled peptidoglycan was not found in cytoplasmic extracts from the ltgA ltgD mutant as it was for the wild-type strain, indicating that generation of anhydro peptidoglycan monomers by lytic transglycosylases facilitates peptidoglycan recycling. The ltgA ltgD double mutant showed no growth abnormalities or cell separation defects, suggesting that these enzymes are involved in pathogenesis but not necessary for normal growth.Peptidoglycan (PG) fragments released during growth contribute to the pathogenesis of multiple bacterial infections, including those of Bordetella pertussis, Helicobacter pylori, and Neisseria gonorrhoeae (6,23,34). PG fragments induce the production of inflammatory cytokines, cause ciliated cell damage and fluid efflux, and trigger the Nod signaling cascade (reviewed in reference 5). Although PG fragments have been studied biochemically and for immunologic effects in multiple systems, the repertoire of genes and enzymes involved in PG fragment production and release from growing bacteria is unknown.PG fragments released from gram-negative bacterial pathogens are predicted to be produced by the action of lytic transglycosylases. Lytic transglycosylases cleave the N-acetylmuramic acid-␤-1,4-N-acetylglucosamine linkage in PG and catalyze the formation of a 1,6-anhydro bond on the N-acetylmuramic acid (16). PG monomers released from N. gonorrhoeae and B. pertussis were shown to have the 1,6-anhydro bond, indicating that they were generated by lytic transglycosylases (26, 30). To identify genes for PG monomer production, we systematically mutated the genes for lytic transglycosylase homologues in N. gonorrhoeae. Mutation of lytic transglycosylase A (ltgA) resulted in a substantial decrease in PG monomers released (3). Mutations in lytic transglycosylase B (ltgB) or lytic transglycosylase C (ltgC) genes had no effect on PG monomer release (4, 19), although the ltgC mutant showed a severe defect in cell separation. These findings suggested the presence of other lytic transglycosylases in N. gonorrhoeae involved in release of PG monomers.Here we show that lytic transglycosylase LtgD is involved in the release of PG monomers. Additionally, we generated and characterized an N. gonorrhoeae strain deleted for both ltgA and...

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Section: Discussionsupporting

confidence: 62%

Section: Resultsmentioning

confidence: 99%

Neisseria gonorrhoeae Uses Two Lytic Transglycosylases To Produce Cytotoxic Peptidoglycan Monomers

et al. 2008

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“…10 In Helicobacter pylori the MltD homologue is thought to act as an endo-type LT. Also, an mltD mutant showed decreased autolysis in stationary-phase culture. 7 It is unknown whether the gonococcal ltgE mutant is affected in these processes.…”

Section: Lts Of Unknown Function: Ltgb and Ltgementioning

confidence: 99%

The Lytic Transglycosylases ofNeisseria gonorrhoeae

Chan

Hackett

Dillard

2012

Microbial Drug Resistance

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“…The insertion of a flagellum would require a localized rearrangement of the PG layer involving endo-activity rather than the processive release of 1,6-anhydroMurNAc products that accompany its turnover during biosynthesis. This type of functional specificity involving the rearrangement of the sacculus has been ascribed to H. pylori MltD (39).…”

Section: Discussionmentioning

confidence: 99%

Modulation of the Lytic Activity of the Dedicated Autolysin for Flagellum Formation SltF by Flagellar Rod Proteins FlgB and FlgF

et al. 2016

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SltF was identified previously as an autolysin required for the assembly of flagella in the alphaproteobacteria, but the nature of its peptidoglycan lytic activity remained unknown. Sequence alignment analyses suggest that it could function as either a muramidase, lytic transglycosylase, or ␤-N-acetylglucosaminidase. Recombinant SltF from Rhodobacter sphaeroides was purified to apparent homogeneity, and it was demonstrated to function as a lytic transglycosylase based on enzymatic assays involving mass spectrometric analyses. Circular dichroism (CD) analysis determined that it is composed of 83.4% ␣-structure and 1.48% ␤-structure and thus is similar to family 1A lytic transglycosylases. However, alignment of apparent SltF homologs identified in the genome database defined a new subfamily of the family 1 lytic transglycosylases. SltF was demonstrated to be endo-acting, cleaving within chains of peptidoglycan, with optimal activity at pH 7.0. Its activity is modulated by two flagellar rod proteins, FlgB and FlgF: FlgB both stabilizes and stimulates SltF activity, while FlgF inhibits it. Invariant Glu57 was confirmed as the sole catalytic acid/base residue of SltF. IMPORTANCEThe bacterial flagellum is comprised of a basal body, hook, and helical filament, which are connected by a rod structure. With a diameter of approximately 4 nm, the rod is larger than the estimated pore size within the peptidoglycan sacculus, and hence its insertion requires the localized and controlled lysis of this essential cell wall component. In many beta-and gammaproteobacteria, this lysis is catalyzed by the ␤-N-acetylglucosaminidase domain of FlgJ. However, FlgJ of the alphaproteobacteria lacks this activity and instead it recruits a separate enzyme, SltF, for this purpose. In this study, we demonstrate that SltF functions as a newly identified class of lytic transglycosylases and that its autolytic activity is uniquely modulated by two rod proteins, FlgB and FlgF.T he photosynthetic bacterium Rhodobacter sphaeroides is motile through the use of a single, subpolar flagellum (1). This locomotive organelle is tightly regulated and comprised of approximately 25 different proteins arranged into three major substructures: a basal body, hook, and thin helical filament. The basal body spans the bacterial cell envelope and contains the motor, a flagellum-specific type III export apparatus and at least four ringlike structures which are all connected by a filamentous rod (2). The rod assembles into a proximal rod that lies between the MS ring and the cell wall, which is composed of nine subunits of FliE (3) and six subunits of FlgB, FlgC, and FlgF (4), as well as a distal rod that is composed of 26 subunits of FlgG (5).During flagellum assembly, extensive modifications need to occur to the peptidoglycan (PG) sacculus to accommodate the insertion of the secretion apparatus, as well as to stabilize the function of this system by acting as an assembly scaffold (6, 7). PG is a heteropolymer of glycan strands and peptide chains forming a rig...

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Characterization ofHelicobacter pyloriLytic Transglycosylases Slt and MltD

Cited by 48 publications

References 24 publications

Neisseria gonorrhoeae Uses Two Lytic Transglycosylases To Produce Cytotoxic Peptidoglycan Monomers

Neisseria gonorrhoeae Uses Two Lytic Transglycosylases To Produce Cytotoxic Peptidoglycan Monomers

The Lytic Transglycosylases ofNeisseria gonorrhoeae

Modulation of the Lytic Activity of the Dedicated Autolysin for Flagellum Formation SltF by Flagellar Rod Proteins FlgB and FlgF

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