2d05

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Revision as of 07:15, 21 November 2007

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spinqualitylabelsall models 2d05, resolution 2.0Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Chitosanase From Bacillus circulans mutant K218P

Overview

To identify the amino acids responsible for the substrate binding of, chitosanase from Bacillus circulans MH-K1 (MH-K1 chitosanase), Tyr148 and, Lys218 of the chitosanase were mutated to serine and proline, respectively, and the mutated chitosanases were characterized. The, enzymatic activities of Y148S and K218P were found to be 12.5% and 0.16%, of the wild type, respectively. When the (GlcN)3 binding ability to the, chitosanase was evaluated by fluorescence spectroscopy and thermal, unfolding experiments, the binding abilities of both mutant enzymes were, markedly reduced as compared with the wild type enzyme. The affinity of, the enzyme for the trisaccharide decreased by 1.0 kcal/mol of binding free, energy for Y148S, and 3.7 kcal/mol for K218P. The crystal structure of, K218P revealed that Pro218 forms a cis-peptide bond and that the state of, the flexible loop containing the 218th residue is considerably affected by, the mutation. Thus, we conclude that the flexible loop containing Lys218, plays an important role in substrate binding, and that the role of Tyr148, is less critical, but still important, due to a stacking interaction or, hydrogen bond.

About this Structure

2D05 is a Single protein structure of sequence from Bacillus circulans with SO4 as ligand. Active as Chitosanase, with EC number 3.2.1.132 Full crystallographic information is available from OCA.

Reference

Bacillus circulans MH-K1 chitosanase: amino acid residues responsible for substrate binding., Fukamizo T, Amano S, Yamaguchi K, Yoshikawa T, Katsumi T, Saito J, Suzuki M, Miki K, Nagata Y, Ando A, J Biochem (Tokyo). 2005 Nov;138(5):563-9. PMID:16272568

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