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Inhibition of Helicobacter pylori adherence by a peptide derived from neuraminyl lactose binding adhesin
Authors:Chaturvedi  G  Tewari  R  Mrigank  M  Agnihotri  N  Vishwakarma  RA  Ganguly  NK
Institution:(1) Department of Microbiology, Panjab University, Chandigarh, India;(2) Bioinformatics Center, Institute of Microbial Technology, Chandigarh, India;(3) Department of Experimental Medicine and Biotechnology, Postgraduate Institute of Medical Education and Research, Chandigarh, India;(4) Bio-organic Chemistry Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, NewDelhi, India;(5) Indian Council of Medical Research, Ansari Nagar, New Delhi –, 110 029, India
Abstract:Helicobacter pylori, like many other gut colonizing bacteria, binds to sialic acid rich macromolecules present on the gastric epithelium. NLBH (neuraminyl lactose binding haemagglutinin) a 32 kDa adhesin located on the surface of H. pylori has been shown to have specific affinity towards NeuAcagr2,3Galbeta1,4Gluc(3primeSL). This sialic acid moiety is over-expressed in an atrophic stomach undergoing parietal cell depletion. Antibodies against a lysine rich peptide fragment of NLBH inhibit agglutination of human erythrocytes. This lysine rich sequence from NLBH was proposed to be the receptor-binding site. In order to elucidate the binding of NLBH to gastric epithelium, a peptide (D-P-K-R-T-I-Q-K-K-S) was synthesized. A series of experiments were performed involving adherence inhibition assays, 2D-NMR, molecular modelling and measurement of modulation in acid secretion. Results indicated that the peptide fragment could be involved in receptor recognition, which is important for the binding of H. pylori to gastric epithelium. The binding is possibly through hydrogen bonding. Two lysines and a threonine residue seem to be within the hydrogen bonding distance of NeuAcagr2,3Galbeta1,4Gluc. Further, in vitro assays were performed to evaluate the role of the peptide on acid secretion by parietal cells isolated from human fundal biopsies. Interestingly, the peptide increases acid secretion only in H. pylori negative and in treated patients but not in H. pylori positive patients. This highlights the role of NLBH in acid secretion and could be of some consequence in the prognosis of the disease.
Keywords:H  pylori  NeuAcagr2" target="_blank">gif" alt="agr" align="BASELINE" BORDER="0">2  3Galbeta1" target="_blank">gif" alt="beta" align="MIDDLE" BORDER="0">1  4Gluc  adhesin  parietal cells  2D-NMR  molecular modelling
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