1pc8
Crystal Structure of a novel form of mistletoe lectin from Himalayan Viscum album L. at 3.8A resolutionCrystal Structure of a novel form of mistletoe lectin from Himalayan Viscum album L. at 3.8A resolution
Structural highlights
FunctionML4_VISAL The A chain is responsible for inhibiting protein synthesis through the catalytic inactivation of 60S ribosomal subunits by removing adenine from position 4,324 of 28S rRNA. The B chain binds to cell receptors and probably facilitates the entry into the cell of the A chain; B chains are also responsible for cell agglutination (lectin activity). Inhibits growth of the human tumor cell line Molt4.[1] [2] [UniProtKB:P81446] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThis is the first report of the structural studies of a novel ribosome-inactivating protein (RIP) obtained from the Himalayan mistletoe (Viscum album) (HmRip). HmRip is a type II heterodimeric protein consisting of a toxic enzyme (A-chain) with an active site for ribosome inactivation and a lectin subunit (B-chain) with well defined sugar-binding sites. The crystal structure of HmRip has been determined at 3.8 A resolution and refined to a crystallographic R factor of 0.228 (R(free) = 0.271). A comparison of this structure with other type II RIPs reveals the presence of distinct structural features in the active site of the A-chain and in the 2gamma sugar-binding site of the B-chain. The conformation of the side chain of Tyr110, which is a conserved active-site residue in the A subunit, is strikingly different from those observed in other mistletoe RIPs, indicating its unique substrate-binding preference. The deletion of two important residues from the kink region after Ala231 in the 2gamma subdomain of the B-chain results in a significantly different conformation of the sugar-binding pocket. A ribosome-recognition site has also been identified in HmRip. The site is a shallow cavity, with the conserved residues Arg51, Asp70, Thr72 and Asn73 involved in the binding. The conformations of the antigenic epitopes of residues 1-20, 85-103 and 206-223 differ from those observed in other type II RIPs, resulting in the distinct antigenicity and pharmacological properties of HmRip. Structure of a novel ribosome-inactivating protein from a hemi-parasitic plant inhabiting the northwestern Himalayas.,Mishra V, Ethayathulla AS, Sharma RS, Yadav S, Krauspenhaar R, Betzel C, Babu CR, Singh TP Acta Crystallogr D Biol Crystallogr. 2004 Dec;60(Pt 12 Pt 2):2295-304., Epub 2004 Nov 26. PMID:15583377[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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