- From Genome to Proteome to Elucidation of Reactions for All Eleven Known Lytic Transglycosylases from Pseudomonas aeruginosa
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An enzyme superfamily, the lytic transglycosylases (LTs), occupies the space between the two membranes of Gram-negative bacteria. LTs catalyze the non-hydrolytic cleavage of the bacterial peptidoglycan cell-wall polymer. This reaction is central to the growth of the cell wall, for excavating the cell wall for protein insertion, and for monitoring the cell wall so as to initiate resistance responses to cell-wall-acting antibiotics. The nefarious Gram-negative pathogen Pseudomonas aeruginosa encodes eleven LTs. With few exceptions, their substrates and functions are unknown. Each P. aeruginosa LT was expressed as a soluble protein and evaluated with a panel of substrates (both simple and complex mimetics of their natural substrates). Thirty-one distinct products distinguish these LTs with respect to substrate recognition, catalytic activity, and relative exolytic or endolytic ability. These properties are foundational to an understanding of the LTs as catalysts and as antibiotic targets.
- Lee, Mijoon,Hesek, Dusan,Dik, David A.,Fishovitz, Jennifer,Lastochkin, Elena,Boggess, Bill,Fisher, Jed F.,Mobashery, Shahriar
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- Synthesis of diaminopimelic acid containing peptidoglycan fragments and tracheal cytotoxin (TCT) and investigation of their biological functions
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Bacterial cell wall peptidoglycan (PGN) is a potent immunostimulator and immune adjuvant. The PGN of Gram-negative bacteria and some Gram-positive bacteria contain meso-diaminopimelic acid (meso-DAP), and we have recently shown that the intracellular protein Nodi is a PGN receptor and recognizes DAPcontaining peptides. In this study, we achieved the synthesis of DAP-containing PGN fragments, including the first chemical synthesis of tracheal cytotoxin (TCT), GlcNAc-(β1-4)-(anhydro) Mur-NAc-L-Ala-γ-D-Glu-meso- DAP-D-Ala, and a repeating-unit of DAP-type PGN, GlcNAc-(β1-4)-MurNAc-L- Ala-γ-D-Glu-meso-DAP-D-Ala. For the synthesis of PGN fragments, we first established a new synthetic method for an orthogonally protected meso-DAP derivative, and then we constructed the glycopeptide structures. The ability of these fragments to stimulate human Nodi, as well as differences in Nodi recognition of the variety of synthesized ligand structures were examined. The results showed that the substitution of the N terminus of iE-DAP is necessary for stronger Nodi recognition, but the structure of the substituent seems not to be strictly recognized. The importance of the carboxyl group at the 2-position of DAP for human Nod1 stimulation was also shown.
- Kawasaki, Akiko,Karasudani, Yukie,Otsuka, Yuji,Hasegawa, Mizuho,Inohara, Naohiro,Fujimoto, Yukari,Fukase, Koichi
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experimental part
p. 10318 - 10330
(2009/11/30)
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