1ex1
From Proteopedia
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'''BETA-D-GLUCAN EXOHYDROLASE FROM BARLEY''' | '''BETA-D-GLUCAN EXOHYDROLASE FROM BARLEY''' | ||
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[[Category: Hrmova, M.]] | [[Category: Hrmova, M.]] | ||
[[Category: Varghese, J N.]] | [[Category: Varghese, J N.]] | ||
| - | [[Category: | + | [[Category: Cell wall degradation]] |
| - | [[Category: | + | [[Category: Hydrolase]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 15:37:09 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 12:37, 2 May 2008
BETA-D-GLUCAN EXOHYDROLASE FROM BARLEY
Overview
BACKGROUND: Cell walls of the starchy endosperm and young vegetative tissues of barley (Hordeum vulgare) contain high levels of (1-->3,1-->4)-beta-D-glucans. The (1-->3,1-->4)-beta-D-glucans are hydrolysed during wall degradation in germinated grain and during wall loosening in elongating coleoptiles. These key processes of plant development are mediated by several polysaccharide endohydrolases and exohydrolases. RESULTS:. The three-dimensional structure of barley beta-D-glucan exohydrolase isoenzyme ExoI has been determined by X-ray crystallography. This is the first reported structure of a family 3 glycosyl hydrolase. The enzyme is a two-domain, globular protein of 605 amino acid residues and is N-glycosylated at three sites. The first 357 residues constitute an (alpha/beta)8 TIM-barrel domain. The second domain consists of residues 374-559 arranged in a six-stranded beta sandwich, which contains a beta sheet of five parallel beta strands and one antiparallel beta strand, with three alpha helices on either side of the sheet. A glucose moiety is observed in a pocket at the interface of the two domains, where Asp285 and Glu491 are believed to be involved in catalysis. CONCLUSIONS: The pocket at the interface of the two domains is probably the active site of the enzyme. Because amino acid residues that line this active-site pocket arise from both domains, activity could be regulated through the spatial disposition of the domains. Furthermore, there are sites on the second domain that may bind carbohydrate, as suggested by previously published kinetic data indicating that, in addition to the catalytic site, the enzyme has a second binding site specific for (1-->3, 1-->4)-beta-D-glucans.
About this Structure
1EX1 is a Single protein structure of sequence from Hordeum vulgare. Full crystallographic information is available from OCA.
Reference
Three-dimensional structure of a barley beta-D-glucan exohydrolase, a family 3 glycosyl hydrolase., Varghese JN, Hrmova M, Fincher GB, Structure. 1999 Feb 15;7(2):179-90. PMID:10368285 Page seeded by OCA on Fri May 2 15:37:09 2008
