2ecp: Difference between revisions
New page: left|200px<br /><applet load="2ecp" size="450" color="white" frame="true" align="right" spinBox="true" caption="2ecp, resolution 2.95Å" /> '''THE CRYSTAL STRUCTUR... |
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[[Image:2ecp.jpg|left|200px]]<br /><applet load="2ecp" size=" | [[Image:2ecp.jpg|left|200px]]<br /><applet load="2ecp" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="2ecp, resolution 2.95Å" /> | caption="2ecp, resolution 2.95Å" /> | ||
'''THE CRYSTAL STRUCTURE OF THE E. COLI MALTODEXTRIN PHOSPHORYLASE COMPLEX'''<br /> | '''THE CRYSTAL STRUCTURE OF THE E. COLI MALTODEXTRIN PHOSPHORYLASE COMPLEX'''<br /> | ||
==Overview== | ==Overview== | ||
Acarbose is a naturally occurring pseudo-tetrasaccharide. It has been used | Acarbose is a naturally occurring pseudo-tetrasaccharide. It has been used in conjunction with other drugs in the treatment of diabetes where it acts as an inhibitor of intestinal glucosidases. To probe the interactions of acarbose with other carbohydrate recognition enzymes, the crystal structure of E. coli maltodextrin phosphorylase (MalP) complexed with acarbose has been determined at 2.95 A resolution and refined to crystallographic R-values of R (Rfree) = 0.241 (0.293), respectively. Acarbose adopts a conformation that is close to its major minimum free energy conformation in the MalP-acarbose structure. The acarviosine moiety of acarbose occupies sub-sites +1 and +2 and the disaccharide sub-sites +3 and +4. (The site of phosphorolysis is between sub-sites -1 and +1.) This is the first identification of sub-sites +3 and +4 of MalP. Interactions of the glucosyl residues in sub-sites +2 and +4 are dominated by carbohydrate stacking interactions with tyrosine residues. These tyrosines (Tyr280 and Tyr613, respectively, in the rabbit muscle phosphorylase numbering scheme) are conserved in all species of phosphorylase. A glycerol molecule from the cryoprotectant occupies sub-site -1. The identification of four oligosaccharide sub-sites, that extend from the interior of the phosphorylase close to the catalytic site to the exterior surface of MalP, provides a structural rationalization of the substrate selectivity of MalP for a pentasaccharide substrate. Crystallographic binding studies of acarbose with amylases, glucoamylases, and glycosyltranferases and NMR studies of acarbose in solution have shown that acarbose can adopt two different conformations. This flexibility allows acarbose to target a number of different enzymes. The two alternative conformations of acarbose when bound to different carbohydrate enzymes are discussed. | ||
==About this Structure== | ==About this Structure== | ||
2ECP is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with ACR, PLP and GOL as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Phosphorylase Phosphorylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.1 2.4.1.1] Full crystallographic information is available from [http:// | 2ECP is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=ACR:'>ACR</scene>, <scene name='pdbligand=PLP:'>PLP</scene> and <scene name='pdbligand=GOL:'>GOL</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Phosphorylase Phosphorylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.1 2.4.1.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2ECP OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Phosphorylase]] | [[Category: Phosphorylase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Johnson, L | [[Category: Johnson, L N.]] | ||
[[Category: Reilly, M | [[Category: Reilly, M O.]] | ||
[[Category: Watson, K | [[Category: Watson, K A.]] | ||
[[Category: ACR]] | [[Category: ACR]] | ||
[[Category: GOL]] | [[Category: GOL]] | ||
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[[Category: phosphorylase]] | [[Category: phosphorylase]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:08:38 2008'' | ||
Revision as of 18:08, 21 February 2008
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THE CRYSTAL STRUCTURE OF THE E. COLI MALTODEXTRIN PHOSPHORYLASE COMPLEX
OverviewOverview
Acarbose is a naturally occurring pseudo-tetrasaccharide. It has been used in conjunction with other drugs in the treatment of diabetes where it acts as an inhibitor of intestinal glucosidases. To probe the interactions of acarbose with other carbohydrate recognition enzymes, the crystal structure of E. coli maltodextrin phosphorylase (MalP) complexed with acarbose has been determined at 2.95 A resolution and refined to crystallographic R-values of R (Rfree) = 0.241 (0.293), respectively. Acarbose adopts a conformation that is close to its major minimum free energy conformation in the MalP-acarbose structure. The acarviosine moiety of acarbose occupies sub-sites +1 and +2 and the disaccharide sub-sites +3 and +4. (The site of phosphorolysis is between sub-sites -1 and +1.) This is the first identification of sub-sites +3 and +4 of MalP. Interactions of the glucosyl residues in sub-sites +2 and +4 are dominated by carbohydrate stacking interactions with tyrosine residues. These tyrosines (Tyr280 and Tyr613, respectively, in the rabbit muscle phosphorylase numbering scheme) are conserved in all species of phosphorylase. A glycerol molecule from the cryoprotectant occupies sub-site -1. The identification of four oligosaccharide sub-sites, that extend from the interior of the phosphorylase close to the catalytic site to the exterior surface of MalP, provides a structural rationalization of the substrate selectivity of MalP for a pentasaccharide substrate. Crystallographic binding studies of acarbose with amylases, glucoamylases, and glycosyltranferases and NMR studies of acarbose in solution have shown that acarbose can adopt two different conformations. This flexibility allows acarbose to target a number of different enzymes. The two alternative conformations of acarbose when bound to different carbohydrate enzymes are discussed.
About this StructureAbout this Structure
2ECP is a Single protein structure of sequence from Escherichia coli with , and as ligands. Active as Phosphorylase, with EC number 2.4.1.1 Full crystallographic information is available from OCA.
ReferenceReference
The crystal structure of the Escherichia coli maltodextrin phosphorylase-acarbose complex., O'Reilly M, Watson KA, Johnson LN, Biochemistry. 1999 Apr 27;38(17):5337-45. PMID:10220320
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