1uuq
From Proteopedia
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'''EXO-MANNOSIDASE FROM CELLVIBRIO MIXTUS''' | '''EXO-MANNOSIDASE FROM CELLVIBRIO MIXTUS''' | ||
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[[Category: Prates, J A.M.]] | [[Category: Prates, J A.M.]] | ||
[[Category: Vincent, F.]] | [[Category: Vincent, F.]] | ||
| - | [[Category: | + | [[Category: Family 5]] |
| - | [[Category: | + | [[Category: Glycoside hydrolase]] |
| - | [[Category: | + | [[Category: Mannan]] |
| - | [[Category: | + | [[Category: Mannosidase]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 11:43:07 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 08:43, 3 May 2008
EXO-MANNOSIDASE FROM CELLVIBRIO MIXTUS
Overview
The enzymatic hydrolysis of the glycosidic bond is central to numerous biological processes. Glycoside hydrolases, which catalyze these reactions, are grouped into families based on primary sequence similarities. One of the largest glycoside hydrolase families is glycoside hydrolase family 5 (GH5), which contains primarily endo-acting enzymes that hydrolyze beta-mannans and beta-glucans. Here we report the cloning, characterization, and three-dimensional structure of the Cellvibrio mixtus GH5 beta-mannosidase (CmMan5A). This enzyme releases mannose from the nonreducing end of mannooligosaccharides and polysaccharides, an activity not previously observed in this enzyme family. CmMan5A contains a single glycone (-1) and two aglycone (+1 and +2) sugar-binding subsites. The -1 subsite displays absolute specificity for mannose, whereas the +1 subsite does not accommodate galactosyl side chains but will bind weakly to glucose. The +2 subsite is able to bind to decorated mannose residues. CmMan5A displays similar activity against crystalline and amorphous mannans, a property rarely attributed to glycoside hydrolases. The 1.5 A crystal structure reveals that CmMan5A adopts a (beta/alpha)(8) barrel fold, and superimposition with GH5 endo-mannanases shows that dramatic differences in the length of three loops modify the active center accessibility and thus modulate the specificity from endo to exo. The most striking and significant difference is the extended loop between strand beta8 and helix alpha8 comprising residues 378-412. This insertion forms a "double" steric barrier, formed by two short beta-strands that function to "block" the substrate binding cleft at the edge of the -1 subsite forming the "exo" active center topology of CmMan5A.
About this Structure
1UUQ is a Single protein structure of sequence from Cellvibrio mixtus. Full crystallographic information is available from OCA.
Reference
Insights into the molecular determinants of substrate specificity in glycoside hydrolase family 5 revealed by the crystal structure and kinetics of Cellvibrio mixtus mannosidase 5A., Dias FM, Vincent F, Pell G, Prates JA, Centeno MS, Tailford LE, Ferreira LM, Fontes CM, Davies GJ, Gilbert HJ, J Biol Chem. 2004 Jun 11;279(24):25517-26. Epub 2004 Mar 10. PMID:15014076 Page seeded by OCA on Sat May 3 11:43:07 2008
