tailieunhanh - The structure of the saccharide-binding site of concanavalin A

The methyl a-D-mannopyranoside molecule is bound in the Cl chair conformation A from the calcium-binding site and A from the transition metal-binding site. A network of seven hydrogen bonds connects oxygen atoms 0-3, 04, 0-5 and 0-6 of the mannoside to residues Asnl4, Leu99, TyrlO0, Asp208 and Arg228. 0-2 and 0-1 of the mannoside extend into the solvent. 0-2 is hydrogenbonded through a water molecule to an adjacent asymmetric unit. | The EMBO Journal , 1989 The structure of the saccharide-binding site of concanavalin A , ', , (Gilboa)1, , , and Department of Chemistry, University of York, Heslington, York YO1 5DD, UK, 'Department of Biophysics, The Weizman Institute of Science, Rehovot, Israel, 2Department of Physics, University of York, Heslington, York YO1 5DD, UK and 3SERC, Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD, UK Communicated by A complex of concanavalin A with methyl ct-Dmannopyranoside has been crystallized in space group P212121 with a = A, b = A and c = A. X-ray diffraction intensities to A resolution have been collected on a Xentronics/Nicolet area detector. The structure has been solved by molecular replacement where the starting model was based on refined coordinates of an 1222 crystal of saccharide-free concanavalin A. The structure of the saccharide complex was refined by restrained least-squares methods to an Rfactor value of . In this crystal form, the asymmetric unit contains four protein subunits, to each of which a molecule of mannoside is bound in a shallow crevice near the surface of the protein. The methyl a-D-mannopyranoside molecule is bound in the Cl chair conformation A from the calcium-binding site and A from the transition metal-binding site. A network of seven hydrogen bonds connects oxygen atoms 0-3, 04, 0-5 and 0-6 of the mannoside to residues Asnl4, Leu99, TyrlO0, Asp208 and Arg228. 0-2 and 0-1 of the mannoside extend into the solvent. 0-2 is hydrogenbonded through a water molecule to an adjacent asymmetric unit. 0-1 is not involved in any hydrogen bond and there is no fixed position for its methyl substituent. Key words: concanavalin A/electron density map/methyl-aD-mannopyranoside/saccharide binding Introduction The structure of concanavalin A, the saccharide-binding protein of the Jack .