5y97

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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The sequence and structure of snake gourd seed lectin (SGSL), a nontoxic homologue of type II ribosome-inactivating proteins (RIPs), have been determined by mass spectrometry and X-ray crystallography, respectively. As in type II RIPs, the molecule consists of a lectin chain made up of two beta-trefoil domains. The catalytic chain, which is connected through a disulfide bridge to the lectin chain in type II RIPs, is cleaved into two in SGSL. However, the integrity of the three-dimensional structure of the catalytic component of the molecule is preserved. This is the first time that a three-chain RIP or RIP homologue has been observed. A thorough examination of the sequence and structure of the protein and of its interactions with the bound methyl-alpha-galactose indicate that the nontoxicity of SGSL results from a combination of changes in the catalytic and the carbohydrate-binding sites. Detailed analyses of the sequences of type II RIPs of known structure and their homologues with unknown structure provide valuable insights into the evolution of this class of proteins. They also indicate some variability in carbohydrate-binding sites, which appears to contribute to the different levels of toxicity exhibited by lectins from various sources.
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Snake gourd seed lectin (SGSL) is a non-toxic homologue of type II ribosome inactivating proteins (RIPs) which contain a catalytic domain and a lectin domain. Isothermal titration calorimetry (ITC) measurements of the interactions of the protein with LacNAc, Lac, Gal, Me-alpha-Gal were carried out and the crystal structures of the native protein and its complex with Lac were determined. The crystal structure of the Me-alpha-Gal complex has already been determined. While the crystal structure showed the presence of two-sugar binding sites, one on each of the two domains of the lectin chain, ITC measurements indicated the presence of only one binding site. In order to resolve this anomaly, Molecular Dynamics (MD) simulations were carried out on the native protein and on its complexes with Me-alpha-Gal and Lac. Simulations were also performed on the protein after reducing the inter-chain disulphide bridge between the two chains. The crystal structures and the simulations confirmed the robustness of the protein structure, irrespective of the presence or absence of the disulphide bridge. The simulations indicated that although two sites can bind sugar, only the ligand at one site is retained in a dynamic situation. The studies thus bring out the subtle relationship between binding and retention of the ligand.
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The sequence and structure of snake gourd (Trichosanthes anguina) seed lectin, a three-chain nontoxic homologue of type II RIPs.,Sharma A, Pohlentz G, Bobbili KB, Jeyaprakash AA, Chandran T, Mormann M, Swamy MJ, Vijayan M Acta Crystallogr D Biol Crystallogr. 2013 Aug;69(Pt 8):1493-503. doi:, 10.1107/S0907444913010020. Epub 2013 Jul 18. PMID:23897472<ref>PMID:23897472</ref>
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Ligand binding and retention in snake gourd seed lectin (SGSL). A crystallographic, thermodynamic and molecular dynamics study.,Chandran T, Sivaji N, Surolia A, Vijayan M Glycobiology. 2018 Aug 6. pii: 5067403. doi: 10.1093/glycob/cwy072. PMID:30099481<ref>PMID:30099481</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 10:22, 5 September 2018

Crystal structure of snake gourd seed lectin in complex with lactose

5y97, resolution 3.05Å

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