1cf5
From Proteopedia
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BETA-MOMORCHARIN STRUCTURE AT 2.55 A
Overview
Beta-Momorcharin (Mr approximately 29 kDa) is a single-chained, ribosome-inactivating protein (RIP) with a branched hexasaccharide bound, to Asn51. The crystal structure of beta-momorcharin has been determined, using the molecular-replacement method and refined to 2. 55 A resolution., The final structural model gave an R factor of 17. 2% and root-mean-square, deviations of 0.016 A and 1.76 degrees from ideal bond lengths and bond, angles, respectively. beta-Momorcharin contains nine alpha-helices, two, 310 helices and three beta-sheets, and its overall structure is similar to, those of other single-chained RIPs. Residues Tyr70, Tyr109, Glu158 and, Arg161 are expected to define the active site of beta-momorcharin as an, rRNA N-glycosidase. The oligosaccharide is linked to the protein through, an N-glycosidic bond, beta-GlcNAc-(1-N)-Asn51, and stretches from the, surface of the N-terminal domain far from the active site, which suggests, that it should not play a role in enzymatic function. The oligosaccharide, of each beta-momorcharin molecule interacts with the protein through, hydrogen bonds, although in the crystals most of these are intermolecular, interactions with the protein atoms in an adjacent unit cell. This is the, first example of an RIP structure which provides information about the, three-dimensional structure and binding site of the oligosaccharide in the, active chains of RIPs.
About this Structure
1CF5 is a Single protein structure of sequence from Momordica charantia. Full crystallographic information is available from OCA.
Reference
Three-dimensional structure of beta-momorcharin at 2.55 A resolution., Yuan YR, He YN, Xiong JP, Xia ZX, Acta Crystallogr D Biol Crystallogr. 1999 Jun;55(Pt 6):1144-51. PMID:10329776
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