2cxg
From Proteopedia
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==Overview== | ==Overview== | ||
| - | Crystals of cyclodextrin glycosyltransferase (CGTase) from Bacillus | + | Crystals of cyclodextrin glycosyltransferase (CGTase) from Bacillus circulans strain 251 were soaked in buffer solutions containing the pseudotetrasaccharide acarbose, a strong amylase- and CGTase inhibitor. The X-ray structure of the complex was elucidated at 2.5-A resolution with a final crystallographic R value of 15.8% for all data between 8.0 and 2.5 A. Acarbose is bound near the catalytic residues Asp229, Glu257, and Asp328. The carboxylic group of Glu257 is at hydrogen bonding distance from the glycosidic oxygen in the scissile bond between the B and C sugars (residue A is at the nonreducing end of the inhibitor). Asp328 makes hydrogen bonds with the 4-amino-4,6-dideoxyglucose (residue B), and Asp229 is in a close van der Waals contact with the C1 atom of this sugar. From this we conclude that in CGTase Glu257 acts as the proton donor and Asp229 serves as the general base or nucleophile, while Asp328 is involved in substrate binding and may be important for elevating the pKa of Glu257. On the basis of these results it appears that the absence of the C6-hydroxyl group in the B sugar is responsible for the inhibitory properties of acarbose on CGTase. This suggests that the C6-hydroxyl group of this sugar plays an essential role in the catalytic mechanism of CGTase.(ABSTRACT TRUNCATED AT 250 WORDS) |
==About this Structure== | ==About this Structure== | ||
| - | 2CXG is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_circulans Bacillus circulans] with <scene name='pdbligand=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure | + | 2CXG is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_circulans Bacillus circulans] with <scene name='pdbligand=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure supersedes the now removed PDB entry 1CXG. Active as [http://en.wikipedia.org/wiki/Cyclomaltodextrin_glucanotransferase Cyclomaltodextrin glucanotransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.19 2.4.1.19] Known structural/functional Sites: <scene name='pdbsite=CA1:First+Ca+Binding+Site'>CA1</scene>, <scene name='pdbsite=CA2:Second+Ca+Binding+Site'>CA2</scene>, <scene name='pdbsite=CAT:Catalytic+Residues'>CAT</scene>, <scene name='pdbsite=MB1:First+Maltose+Binding+Site.+Note+This+Site+Also+Contains+...'>MB1</scene>, <scene name='pdbsite=MB2:Second+Maltose+Binding+Site'>MB2</scene> and <scene name='pdbsite=MB3:Third+Maltose+Binding+Site.+Note+This+Site+Also+Contains+...'>MB3</scene>. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2CXG OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Cyclomaltodextrin glucanotransferase]] | [[Category: Cyclomaltodextrin glucanotransferase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Dijkstra, B | + | [[Category: Dijkstra, B W.]] |
[[Category: Ruiterkamp, R.]] | [[Category: Ruiterkamp, R.]] | ||
| - | [[Category: Strokopytov, B | + | [[Category: Strokopytov, B V.]] |
| - | [[Category: Uitdehaag, J | + | [[Category: Uitdehaag, J C.M.]] |
[[Category: CA]] | [[Category: CA]] | ||
[[Category: glycosyltransferase]] | [[Category: glycosyltransferase]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:53:23 2008'' |
Revision as of 14:53, 21 February 2008
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CYCLODEXTRIN GLYCOSYLTRANSFERASE COMPLEXED TO THE INHIBITOR ACARBOSE
Overview
Crystals of cyclodextrin glycosyltransferase (CGTase) from Bacillus circulans strain 251 were soaked in buffer solutions containing the pseudotetrasaccharide acarbose, a strong amylase- and CGTase inhibitor. The X-ray structure of the complex was elucidated at 2.5-A resolution with a final crystallographic R value of 15.8% for all data between 8.0 and 2.5 A. Acarbose is bound near the catalytic residues Asp229, Glu257, and Asp328. The carboxylic group of Glu257 is at hydrogen bonding distance from the glycosidic oxygen in the scissile bond between the B and C sugars (residue A is at the nonreducing end of the inhibitor). Asp328 makes hydrogen bonds with the 4-amino-4,6-dideoxyglucose (residue B), and Asp229 is in a close van der Waals contact with the C1 atom of this sugar. From this we conclude that in CGTase Glu257 acts as the proton donor and Asp229 serves as the general base or nucleophile, while Asp328 is involved in substrate binding and may be important for elevating the pKa of Glu257. On the basis of these results it appears that the absence of the C6-hydroxyl group in the B sugar is responsible for the inhibitory properties of acarbose on CGTase. This suggests that the C6-hydroxyl group of this sugar plays an essential role in the catalytic mechanism of CGTase.(ABSTRACT TRUNCATED AT 250 WORDS)
About this Structure
2CXG is a Single protein structure of sequence from Bacillus circulans with as ligand. This structure supersedes the now removed PDB entry 1CXG. Active as Cyclomaltodextrin glucanotransferase, with EC number 2.4.1.19 Known structural/functional Sites: , , , , and . Full crystallographic information is available from OCA.
Reference
X-ray structure of cyclodextrin glycosyltransferase complexed with acarbose. Implications for the catalytic mechanism of glycosidases., Strokopytov B, Penninga D, Rozeboom HJ, Kalk KH, Dijkhuizen L, Dijkstra BW, Biochemistry. 1995 Feb 21;34(7):2234-40. PMID:7857935
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