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Structural basis of sugar-recognizing ubiquitin ligase

Overview

SCF(Fbs1) is a ubiquitin ligase that functions in the endoplasmic, reticulum (ER)-associated degradation pathway. Fbs1/Fbx2, a member of the, F-box proteins, recognizes high-mannose oligosaccharides. Efficient, binding to an N-glycan requires di-N-acetylchitobiose (chitobiose). Here, we report the crystal structures of the sugar-binding domain (SBD) of Fbs1, alone and in complex with chitobiose. The SBD is composed of a, ten-stranded antiparallel beta-sandwich. The structure of the, SBD-chitobiose complex includes hydrogen bonds between Fbs1 and chitobiose, and insertion of the methyl group of chitobiose into a small hydrophobic, pocket of Fbs1. Moreover, NMR spectroscopy has demonstrated that the amino, acid residues adjoining the chitobiose-binding site interact with the, outer branches of the carbohydrate moiety. Considering that the innermost, chitobiose moieties in N-glycans are usually involved in intramolecular, interactions with the polypeptide moieties, we propose that Fbs1 interacts, with the chitobiose in unfolded N-glycoprotein, pointing the protein, moiety toward E2 for ubiquitination.

About this Structure

1UMH is a Single protein structure of sequence from Mus musculus with NI as ligand. Active as Ubiquitin--protein ligase, with EC number 6.3.2.19 Full crystallographic information is available from OCA.

Reference

Structural basis of sugar-recognizing ubiquitin ligase., Mizushima T, Hirao T, Yoshida Y, Lee SJ, Chiba T, Iwai K, Yamaguchi Y, Kato K, Tsukihara T, Tanaka K, Nat Struct Mol Biol. 2004 Apr;11(4):365-70. Epub 2004 Feb 29. PMID:14990996

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