1ajr: Difference between revisions

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REFINEMENT AND COMPARISON OF THE CRYSTAL STRUCTURES OF PIG CYTOSOLIC ASPARTATE AMINOTRANSFERASE AND ITS COMPLEX WITH 2-METHYLASPARTATE

OverviewOverview

Two high resolution crystal structures of cytosolic aspartate aminotransferase from pig heart provide additional insights into the stereochemical mechanism for ligand-induced conformational changes in this enzyme. Structures of the homodimeric native structure and its complex with the substrate analog 2-methylaspartate have been refined, respectively, with 1.74-A x-ray diffraction data to an R value of 0.170, and with 1.6-A data to an R value of 0.173. In the presence of 2-methylaspartate, one of the subunits (subunit 1) shows a ligand-induced conformational change that involves a large movement of the small domain (residues 12-49 and 327-412) to produce a "closed" conformation. No such transition is observed in the other subunit (subunit 2), because crystal lattice contacts lock it in an "open" conformation like that adopted by subunit 1 in the absence of substrate. By comparing the open and closed forms of cAspAT, we propose a stereochemical mechanism for the open-to-closed transition that involves the electrostatic neutralization of two active site arginine residues by the negative charges of the incoming substrate, a large change in the backbone (phi,psi) conformational angles of two key glycine residues, and the entropy-driven burial of a stretch of hydrophobic residues on the N-terminal helix. The calculated free energy for the burial of this "hydrophobic plug" appears to be sufficient to serve as the driving force for domain closure.

About this StructureAbout this Structure

1AJR is a Single protein structure of sequence from Sus scrofa. Active as Aspartate transaminase, with EC number 2.6.1.1 Known structural/functional Site: . Full crystallographic information is available from OCA.

ReferenceReference

Refinement and comparisons of the crystal structures of pig cytosolic aspartate aminotransferase and its complex with 2-methylaspartate., Rhee S, Silva MM, Hyde CC, Rogers PH, Metzler CM, Metzler DE, Arnone A, J Biol Chem. 1997 Jul 11;272(28):17293-302. PMID:9211866

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 ==Overview==
-Two high resolution crystal structures of cytosolic aspartate, aminotransferase from pig heart provide additional insights into the, stereochemical mechanism for ligand-induced conformational changes in this, enzyme. Structures of the homodimeric native structure and its complex, with the substrate analog 2-methylaspartate have been refined, respectively, with 1.74-A x-ray diffraction data to an R value of 0.170, and with 1.6-A data to an R value of 0.173. In the presence of, 2-methylaspartate, one of the subunits (subunit 1) shows a ligand-induced, conformational change that involves a large movement of the small domain, (residues 12-49 and 327-412) to produce a "closed" conformation. No such, transition is observed in the other subunit (subunit 2), because crystal, lattice contacts lock it in an "open" conformation like that adopted by, subunit 1 in the absence of substrate. By comparing the open and closed, forms of cAspAT, we propose a stereochemical mechanism for the, open-to-closed transition that involves the electrostatic neutralization, of two active site arginine residues by the negative charges of the, incoming substrate, a large change in the backbone (phi,psi), conformational angles of two key glycine residues, and the entropy-driven, burial of a stretch of hydrophobic residues on the N-terminal helix. The, calculated free energy for the burial of this "hydrophobic plug" appears, to be sufficient to serve as the driving force for domain closure.
+Two high resolution crystal structures of cytosolic aspartate aminotransferase from pig heart provide additional insights into the stereochemical mechanism for ligand-induced conformational changes in this enzyme. Structures of the homodimeric native structure and its complex with the substrate analog 2-methylaspartate have been refined, respectively, with 1.74-A x-ray diffraction data to an R value of 0.170, and with 1.6-A data to an R value of 0.173. In the presence of 2-methylaspartate, one of the subunits (subunit 1) shows a ligand-induced conformational change that involves a large movement of the small domain (residues 12-49 and 327-412) to produce a "closed" conformation. No such transition is observed in the other subunit (subunit 2), because crystal lattice contacts lock it in an "open" conformation like that adopted by subunit 1 in the absence of substrate. By comparing the open and closed forms of cAspAT, we propose a stereochemical mechanism for the open-to-closed transition that involves the electrostatic neutralization of two active site arginine residues by the negative charges of the incoming substrate, a large change in the backbone (phi,psi) conformational angles of two key glycine residues, and the entropy-driven burial of a stretch of hydrophobic residues on the N-terminal helix. The calculated free energy for the burial of this "hydrophobic plug" appears to be sufficient to serve as the driving force for domain closure.
 ==About this Structure==
@@ Line 15: / Line 15: @@
 [[Category: Sus scrofa]]
 [[Category: Arnone, A.]]
-[[Category: Hyde, C.C.]]
+[[Category: Hyde, C C.]]
-[[Category: Metzler, C.M.]]
+[[Category: Metzler, C M.]]
-[[Category: Metzler, D.E.]]
+[[Category: Metzler, D E.]]
 [[Category: Rhee, S.]]
-[[Category: Rogers, P.H.]]
+[[Category: Rogers, P H.]]
-[[Category: Silva, M.M.]]
+[[Category: Silva, M M.]]
 [[Category: aminotransferase]]
 [[Category: cytosolic aspartate aminotransferase]]
@@ Line 26: / Line 26: @@
 [[Category: pig]]
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Feb  3 09:30:38 2008''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:45:17 2008''