1mac
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(New page: 200px<br /><applet load="1mac" size="450" color="white" frame="true" align="right" spinBox="true" caption="1mac, resolution 2.3Å" /> '''CRYSTAL STRUCTURE AND...)
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Revision as of 19:09, 20 November 2007
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CRYSTAL STRUCTURE AND SITE-DIRECTED MUTAGENESIS OF BACILLUS MACERANS ENDO-1,3-1,4-BETA-GLUCANASE
Overview
In beta-glucans those beta-1,4 glycosidic bonds which are adjacent to, beta-1,3 bonds are cleaved by endo-1,3-1,4-beta-glucanases, (beta-glucanases). Here, the relationship between structure and activity, of the beta-glucanase of Bacillus macerans is studied by x-ray, crystallography and site-directed mutagenesis of active site residues., Crystal structure analysis at 2.3-A resolution reveals a jelly-roll, protein structure with a deep active site channel harboring the amino acid, residues Trp101, Glu103, Asp105, and Glu107 as in the hybrid Bacillus, beta-glucanase H(A16-M) (Keitel, T., Simon, O., Borriss, R., and, Heinemann, U. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 5287-5291)., Different mutant proteins with substitutions in these residues are, generated by site-directed mutagenesis, isolated, and characterized., Compared with the wild-type enzyme their activity is reduced to less than, 1%. Several mutants with isosteric substitutions in Glu103 and Glu107 are, completely inactive, suggesting a direct role of these residues in, glycosyl bond hydrolysis. The kinetic properties of mutant beta-glucanases, and the crystal structure of the wild-type enzyme are consistent with a, mechanism where Glu103 and Glu107 are the catalytic amino acid residues, responsible for cleavage of the beta-1,4 glycosidic bond within the, substrate molecule.
About this Structure
1MAC is a Single protein structure of sequence from Paenibacillus macerans with CA as ligand. Active as Licheninase, with EC number 3.2.1.73 Full crystallographic information is available from OCA.
Reference
Crystal structure and site-directed mutagenesis of Bacillus macerans endo-1,3-1,4-beta-glucanase., Hahn M, Olsen O, Politz O, Borriss R, Heinemann U, J Biol Chem. 1995 Feb 17;270(7):3081-8. PMID:7852389
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