1glh
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(New page: 200px<br /><applet load="1glh" size="450" color="white" frame="true" align="right" spinBox="true" caption="1glh, resolution 2.0Å" /> '''CATION BINDING TO A B...)
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Revision as of 14:01, 20 November 2007
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CATION BINDING TO A BACILLUS (1,3-1,4)-BETA-GLUCANASE. GEOMETRY, AFFINITY AND EFFECT ON PROTEIN STABILITY
Overview
The hybrid Bacillus (1,3-1,4)-beta-glucanase H(A16-M), consisting of 16, N-terminal amino acids derived from the mature form of the B., amyloliquefaciens enzyme and of 198 C-proximal amino acids from the B., macerans enzyme, binds a calcium ion at a site at its molecular surface, remote from the active center [T. Keitel, O. Simon, R. Borriss & U., Heinemann (1993) Proc. Natl Acad. Sci. USA 90, 5287-5291]. X-ray, diffraction analysis at 0.22-nm resolution of crystals grown in the, absence of calcium and in the presence of EDTA shows this site to be, occupied by a sodium ion. Whereas the calcium ion has six oxygen atoms in, its coordination sphere, two of which are from water molecules, sodium is, fivefold coordinated with a fifth ligand belonging to a symmetry-related, protein molecule in the crystal lattice. The affinity of H(A16-M) for, calcium over sodium has been determined calorimetrically. Calcium binding, stabilizes the native three-dimensional structure of the protein as shown, by guanidinium chloride unfolding and thermal inactivation experiments., The enhanced enzymic activity of Bacillus beta-glucanases at elevated, temperatures in the presence of calcium ions is attributed to a general, stabilizing effect by the cation.
About this Structure
1GLH is a Single protein structure of sequence from Synthetic construct with NA as ligand. Active as Licheninase, with EC number 3.2.1.73 Full crystallographic information is available from OCA.
Reference
Cation binding to a Bacillus (1,3-1,4)-beta-glucanase. Geometry, affinity and effect on protein stability., Keitel T, Meldgaard M, Heinemann U, Eur J Biochem. 1994 May 15;222(1):203-14. PMID:8200344
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