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1pc8
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(New page: 200px<br /><applet load="1pc8" size="450" color="white" frame="true" align="right" spinBox="true" caption="1pc8, resolution 3.80Å" /> '''Crystal Structure of...)
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Revision as of 21:33, 20 November 2007
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Crystal Structure of a novel form of mistletoe lectin from Himalayan Viscum album L. at 3.8A resolution
Overview
This 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.
About this Structure
1PC8 is a Protein complex structure of sequences from Viscum album with NAG as ligand. Active as rRNA N-glycosylase, with EC number 3.2.2.22 Full crystallographic information is available from OCA.
Reference
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
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