1yna
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(New page: 200px<br /><applet load="1yna" size="450" color="white" frame="true" align="right" spinBox="true" caption="1yna, resolution 1.55Å" /> '''ENDO-1,4-BETA-XYLANA...)
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Revision as of 04:48, 21 November 2007
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ENDO-1,4-BETA-XYLANASE, ROOM TEMPERATURE, PH 4.0
Overview
The crystal structure of the thermostable xylanase from Thermomyces, lanuginosus was determined by single-crystal X-ray diffraction. The, protein crystallizes in space group P21, a = 40.96(4) A, b = 52. 57(5) A, c = 50.47 (5) A, beta = 100.43(5) degrees, Z = 2. Diffraction data were, collected at room temperature for a resolution range of 25-1.55 A, and the, structure was solved by molecular replacement with the coordinates of, xylanase II from Trichoderma reesei as a search model and refined to a, crystallographic R-factor of 0.155 for all observed reflections. The, enzyme belongs to the family 11 of glycosyl hydrolases [Henrissat, B., and, Bairoch, A. (1993) Biochem. J. 293, 781-788]. pKa calculations were, performed to assess the protonation state of residues relevant for, catalysis and enzyme stability, and a heptaxylan was fitted into the, active-site groove by homology modeling, using the published crystal, structure of a complex between the Bacillus circulans xylanase and a, xylotetraose. Molecular dynamics indicated the central three sugar rings, to be tightly bound, whereas the peripheral ones can assume different, orientations and conformations, suggesting that the enzyme might also, accept xylan chains which are branched at these positions. The reasons for, the thermostability of the T. lanuginosus xylanase were analyzed by, comparing its crystal structure with known structures of mesophilic family, 11 xylanases. It appears that the thermostability is due to the presence, of an extra disulfide bridge, as well as to an increase in the density of, charged residues throughout the protein.
About this Structure
1YNA is a Single protein structure of sequence from Thermomyces lanuginosus. Active as Endo-1,4-beta-xylanase, with EC number 3.2.1.8 Full crystallographic information is available from OCA.
Reference
Thermophilic xylanase from Thermomyces lanuginosus: high-resolution X-ray structure and modeling studies., Gruber K, Klintschar G, Hayn M, Schlacher A, Steiner W, Kratky C, Biochemistry. 1998 Sep 29;37(39):13475-85. PMID:9753433
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