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| - | [[Image:1b3x.gif|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_1b3x| PDB=1b3x | SCENE= }} | | {{STRUCTURE_1b3x| PDB=1b3x | SCENE= }} |
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| - | '''XYLANASE FROM PENICILLIUM SIMPLICISSIMUM, COMPLEX WITH XYLOTRIOSE'''
| + | ===XYLANASE FROM PENICILLIUM SIMPLICISSIMUM, COMPLEX WITH XYLOTRIOSE=== |
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| - | ==Overview==
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| - | Following a recent low-temperature crystal structure analysis of the native xylanase from Penicillium simplicissimum [Schmidt et al. (1998) Protein Sci. 7, 2081-2088], where an array of glycerol molecules, diffused into the crystal during soaking in a cryoprotectant, was observed within the active-site cleft, we utilized monomeric xylose as well as a variety of linear (Xn, n = 2 to 5) and branched xylooligomers at high concentrations (typically 20% w/v) as cryoprotectant for low-temperature crystallographic experiments. Binding of the glycosidic moiety (or its hydrolysis products) to the enzyme's active-site cleft was observed after as little as 30 s soaking of a native enzyme crystal. The use of a substrate or substrate analogue as cryoprotectant therefore suggests itself as a simple and widely applicable alternative to the use of crystallographic flow-cells for substrate-saturation experiments. Short-chain xylooligomers, i.e., xylobiose (X2) and xylotriose (X3), were found to bind to the active-site cleft with its reducing end hydrogen-bonded to the catalytic acid-base catalyst Glu132. Xylotetraose (X4) and -pentaose (X5) had apparently been cleaved during the soaking time into a xylotriose plus a monomeric (X4) or dimeric (X5) sugar. While the trimeric hydrolysis product was always found to bind in the same way as xylotriose, the monomer or dimer yielded only weak and diffuse electron density within the xylan-binding cleft, at the opposite side of the active center. This suggests that the two catalytic residues divide the binding cleft into a "substrate recognition area" (from the active site toward the nonreducing end of a bound xylan chain), with strong and specific xylan binding and a "product release area" with considerably weaker and less specific binding. The size of the substrate recognition area (3-4 subsites for sugar rings) explains enzyme kinetic data, according to which short oligomers (X2 and X3) bind to the enzyme without being hydrolyzed.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_10029534}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 10029534 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_10029534}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Penicillium simplicissimum]] | | [[Category: Penicillium simplicissimum]] |
| | [[Category: Substrate binding]] | | [[Category: Substrate binding]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 11:02:09 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 18:11:42 2008'' |
Revision as of 15:11, 30 June 2008
Template:STRUCTURE 1b3x
XYLANASE FROM PENICILLIUM SIMPLICISSIMUM, COMPLEX WITH XYLOTRIOSE
Template:ABSTRACT PUBMED 10029534
About this Structure
1B3X is a Single protein structure of sequence from Penicillium simplicissimum. Full crystallographic information is available from OCA.
Reference
Xylan binding subsite mapping in the xylanase from Penicillium simplicissimum using xylooligosaccharides as cryo-protectant., Schmidt A, Gubitz GM, Kratky C, Biochemistry. 1999 Feb 23;38(8):2403-12. PMID:10029534
Page seeded by OCA on Mon Jun 30 18:11:42 2008
