2fy7
From Proteopedia
(New page: 200px<br /> <applet load="2fy7" size="450" color="white" frame="true" align="right" spinBox="true" caption="2fy7, resolution 1.70Å" /> '''Crystal structure o...) |
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caption="2fy7, resolution 1.70Å" /> | caption="2fy7, resolution 1.70Å" /> | ||
'''Crystal structure of the catalytic domain of the human beta1,4-galactosyltransferase mutant M339H in apo form'''<br /> | '''Crystal structure of the catalytic domain of the human beta1,4-galactosyltransferase mutant M339H in apo form'''<br /> | ||
==Overview== | ==Overview== | ||
| - | During the catalytic cycle of beta1,4-galactosyltransferase-1 (Gal-T1), upon the binding of Mn(2+) followed by UDP-Gal, two flexible loops, a long | + | During the catalytic cycle of beta1,4-galactosyltransferase-1 (Gal-T1), upon the binding of Mn(2+) followed by UDP-Gal, two flexible loops, a long and a short loop, change their conformation from open to closed. We have determined the crystal structures of a human M340H-Gal-T1 mutant in the open conformation (apo-enzyme), its Mn(2+) and Mn(2+)-UDP-Gal-bound complexes, and of a pentenary complex of bovine Gal-T1-Mn(2+)-UDP-GalNAc-Glc-alpha-lactalbumin. These studies show that during the conformational changes in Gal-T1, the coordination of Mn(2+) undergoes significant changes. It loses a coordination bond with a water molecule bound in the open conformation of Gal-T1 while forming a new coordination bond with another water molecule in the closed conformation, creating an active ground-state structure that facilitates enzyme catalysis. In the crystal structure of the pentenary complex, the N-acetylglucosamine (GlcNAc) moiety is found cleaved from UDP-GalNAc and is placed 2.7A away from the O4 oxygen atom of the acceptor Glc molecule, yet to form the product. The anomeric C1 atom of the cleaved GalNAc moiety has only two covalent bonds with its non-hydrogen atoms (O5 and C2 atoms), similar to either an oxocarbenium ion or N-acetylgalactal form, which are crystallographically indistinguishable at the present resolution. The structure also shows that the newly formed, metal-coordinating water molecule forms a hydrogen bond with the beta-phosphate group of the cleaved UDP moiety. This hydrogen bond formation results in the rotation of the beta-phosphate group of UDP away from the cleaved GalNAc moiety, thereby preventing the re-formation of the UDP-sugar during catalysis. Therefore, this water molecule plays an important role during catalysis in ensuring that the catalytic reaction proceeds in a forward direction. |
==Disease== | ==Disease== | ||
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==About this Structure== | ==About this Structure== | ||
| - | 2FY7 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with PGE as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/N-acetyllactosamine_synthase N-acetyllactosamine synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.90 2.4.1.90] Full crystallographic information is available from [http:// | + | 2FY7 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=PGE:'>PGE</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/N-acetyllactosamine_synthase N-acetyllactosamine synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.90 2.4.1.90] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2FY7 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: N-acetyllactosamine synthase]] | [[Category: N-acetyllactosamine synthase]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Qasba, P | + | [[Category: Qasba, P K.]] |
[[Category: Ramakrishnan, B.]] | [[Category: Ramakrishnan, B.]] | ||
[[Category: Ramasamy, V.]] | [[Category: Ramasamy, V.]] | ||
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[[Category: m339h mutant]] | [[Category: m339h mutant]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:26:18 2008'' |
Revision as of 15:26, 21 February 2008
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Crystal structure of the catalytic domain of the human beta1,4-galactosyltransferase mutant M339H in apo form
Contents |
Overview
During the catalytic cycle of beta1,4-galactosyltransferase-1 (Gal-T1), upon the binding of Mn(2+) followed by UDP-Gal, two flexible loops, a long and a short loop, change their conformation from open to closed. We have determined the crystal structures of a human M340H-Gal-T1 mutant in the open conformation (apo-enzyme), its Mn(2+) and Mn(2+)-UDP-Gal-bound complexes, and of a pentenary complex of bovine Gal-T1-Mn(2+)-UDP-GalNAc-Glc-alpha-lactalbumin. These studies show that during the conformational changes in Gal-T1, the coordination of Mn(2+) undergoes significant changes. It loses a coordination bond with a water molecule bound in the open conformation of Gal-T1 while forming a new coordination bond with another water molecule in the closed conformation, creating an active ground-state structure that facilitates enzyme catalysis. In the crystal structure of the pentenary complex, the N-acetylglucosamine (GlcNAc) moiety is found cleaved from UDP-GalNAc and is placed 2.7A away from the O4 oxygen atom of the acceptor Glc molecule, yet to form the product. The anomeric C1 atom of the cleaved GalNAc moiety has only two covalent bonds with its non-hydrogen atoms (O5 and C2 atoms), similar to either an oxocarbenium ion or N-acetylgalactal form, which are crystallographically indistinguishable at the present resolution. The structure also shows that the newly formed, metal-coordinating water molecule forms a hydrogen bond with the beta-phosphate group of the cleaved UDP moiety. This hydrogen bond formation results in the rotation of the beta-phosphate group of UDP away from the cleaved GalNAc moiety, thereby preventing the re-formation of the UDP-sugar during catalysis. Therefore, this water molecule plays an important role during catalysis in ensuring that the catalytic reaction proceeds in a forward direction.
Disease
Known diseases associated with this structure: Congenital disorder of glycosylation, type IId OMIM:[137060]
About this Structure
2FY7 is a Single protein structure of sequence from Homo sapiens with as ligand. Active as N-acetyllactosamine synthase, with EC number 2.4.1.90 Full crystallographic information is available from OCA.
Reference
Structural snapshots of beta-1,4-galactosyltransferase-I along the kinetic pathway., Ramakrishnan B, Ramasamy V, Qasba PK, J Mol Biol. 2006 Apr 14;357(5):1619-33. Epub 2006 Feb 9. PMID:16497331
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