1oxp
From Proteopedia
(New page: 200px<br /><applet load="1oxp" size="450" color="white" frame="true" align="right" spinBox="true" caption="1oxp, resolution 2.5Å" /> '''ASPARTATE AMINOTRANSF...) |
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| - | [[Image:1oxp.jpg|left|200px]]<br /><applet load="1oxp" size=" | + | [[Image:1oxp.jpg|left|200px]]<br /><applet load="1oxp" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1oxp, resolution 2.5Å" /> | caption="1oxp, resolution 2.5Å" /> | ||
'''ASPARTATE AMINOTRANSFERASE, H-ASP COMPLEX, CLOSED CONFORMATION'''<br /> | '''ASPARTATE AMINOTRANSFERASE, H-ASP COMPLEX, CLOSED CONFORMATION'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The interaction of mitochondrial aspartate aminotransferase with | + | The interaction of mitochondrial aspartate aminotransferase with hydroxylamine and five derivatives (in which the hydroxyl hydrogen is replaced by the side chain of naturally occurring amino acids) was investigated by X-ray diffraction as well as by kinetic and spectral measurements with the enzyme in solution. The inhibitors react with pyridoxal 5'-phosphate in the enzyme active site, both in solution and in the crystalline state, in a reversible single-step reaction forming spectrally distinct oxime adducts. Dissociation constants determined in solution range from 10(-8) M to 10(-6) M depending on the nature of the side-chain group. The crystal structures of the adducts of mitochondrial aspartate aminotransferase with the monocarboxylic analogue of L-aspartate in the open and closed enzyme conformation were determined at 0.23-nm and 0.25-nm resolution, respectively. This inhibitor binds to both the open and closed crystal forms of the enzyme without disturbing the crystalline order. Small differences in the conformation of the cofactor pyridoxal phosphate were detected between the omega-carboxylate of the inhibitor and Arg292 of the neighbouring subunit is mainly responsible for the attainment of near-coplanarity of the aldimine bond with the pyridine ring in the oxime adducts. Studies with a fluorescent probe aimed to detect shifts in the open/closed conformational equilibrium of the enzyme in oxime complexes showed that the hydroxylamine-derived inhibitors, even those containing a carboxylate group, do not induce the 'domain closure' in solution. This is probably due to the absence of the alpha-carboxylate group in the monocarboxylic hydroxylamine-derived inhibitors, emphasizing that both carboxylates of the substrates L-Asp and L-Glu are essential for stabilizing the closed form of aspartate aminotransferase. |
==About this Structure== | ==About this Structure== | ||
| - | 1OXP is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus] with IK2 as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Aspartate_transaminase Aspartate transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.1 2.6.1.1] Full crystallographic information is available from [http:// | + | 1OXP is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus] with <scene name='pdbligand=IK2:'>IK2</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Aspartate_transaminase Aspartate transaminase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.6.1.1 2.6.1.1] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1OXP OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Hohenester, E.]] | [[Category: Hohenester, E.]] | ||
| - | [[Category: Jansonius, J | + | [[Category: Jansonius, J N.]] |
[[Category: Schirmer, T.]] | [[Category: Schirmer, T.]] | ||
[[Category: IK2]] | [[Category: IK2]] | ||
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[[Category: vitamin b6]] | [[Category: vitamin b6]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:22:51 2008'' |
Revision as of 12:22, 21 February 2008
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ASPARTATE AMINOTRANSFERASE, H-ASP COMPLEX, CLOSED CONFORMATION
Overview
The interaction of mitochondrial aspartate aminotransferase with hydroxylamine and five derivatives (in which the hydroxyl hydrogen is replaced by the side chain of naturally occurring amino acids) was investigated by X-ray diffraction as well as by kinetic and spectral measurements with the enzyme in solution. The inhibitors react with pyridoxal 5'-phosphate in the enzyme active site, both in solution and in the crystalline state, in a reversible single-step reaction forming spectrally distinct oxime adducts. Dissociation constants determined in solution range from 10(-8) M to 10(-6) M depending on the nature of the side-chain group. The crystal structures of the adducts of mitochondrial aspartate aminotransferase with the monocarboxylic analogue of L-aspartate in the open and closed enzyme conformation were determined at 0.23-nm and 0.25-nm resolution, respectively. This inhibitor binds to both the open and closed crystal forms of the enzyme without disturbing the crystalline order. Small differences in the conformation of the cofactor pyridoxal phosphate were detected between the omega-carboxylate of the inhibitor and Arg292 of the neighbouring subunit is mainly responsible for the attainment of near-coplanarity of the aldimine bond with the pyridine ring in the oxime adducts. Studies with a fluorescent probe aimed to detect shifts in the open/closed conformational equilibrium of the enzyme in oxime complexes showed that the hydroxylamine-derived inhibitors, even those containing a carboxylate group, do not induce the 'domain closure' in solution. This is probably due to the absence of the alpha-carboxylate group in the monocarboxylic hydroxylamine-derived inhibitors, emphasizing that both carboxylates of the substrates L-Asp and L-Glu are essential for stabilizing the closed form of aspartate aminotransferase.
About this Structure
1OXP is a Single protein structure of sequence from Gallus gallus with as ligand. Active as Aspartate transaminase, with EC number 2.6.1.1 Full crystallographic information is available from OCA.
Reference
Crystal structures and solution studies of oxime adducts of mitochondrial aspartate aminotransferase., Markovic-Housley Z, Schirmer T, Hohenester E, Khomutov AR, Khomutov RM, Karpeisky MY, Sandmeier E, Christen P, Jansonius JN, Eur J Biochem. 1996 Mar 15;236(3):1025-32. PMID:8665890
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