1akc: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
[[Image:1akc.gif|left|200px]] | [[Image:1akc.gif|left|200px]] | ||
'''STRUCTURAL BASIS FOR THE CATALYTIC ACTIVITY OF ASPARTATE AMINOTRANSFERASE K258H LACKING ITS PYRIDOXAL-5'-PHOSPHATE-BINDING LYSINE RESIDUE''' | {{Structure | ||
|PDB= 1akc |SIZE=350|CAPTION= <scene name='initialview01'>1akc</scene>, resolution 2.3Å | |||
|SITE= | |||
|LIGAND= <scene name='pdbligand=PPE:4-[(1,3-DICARBOXY-PROPYLAMINO)-METHYL]-3-HYDROXY-2-METHYL-5-PHOSPHONOOXYMETHYL-PYRIDINIUM'>PPE</scene> | |||
|ACTIVITY= [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] | |||
|GENE= | |||
}} | |||
'''STRUCTURAL BASIS FOR THE CATALYTIC ACTIVITY OF ASPARTATE AMINOTRANSFERASE K258H LACKING ITS PYRIDOXAL-5'-PHOSPHATE-BINDING LYSINE RESIDUE''' | |||
==Overview== | ==Overview== | ||
| Line 7: | Line 16: | ||
==About this Structure== | ==About this Structure== | ||
1AKC is a [ | 1AKC is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Gallus_gallus Gallus gallus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AKC OCA]. | ||
==Reference== | ==Reference== | ||
Structural basis for the catalytic activity of aspartate aminotransferase K258H lacking the pyridoxal 5'-phosphate-binding lysine residue., Malashkevich VN, Jager J, Ziak M, Sauder U, Gehring H, Christen P, Jansonius JN, Biochemistry. 1995 Jan 17;34(2):405-14. PMID:[http:// | Structural basis for the catalytic activity of aspartate aminotransferase K258H lacking the pyridoxal 5'-phosphate-binding lysine residue., Malashkevich VN, Jager J, Ziak M, Sauder U, Gehring H, Christen P, Jansonius JN, Biochemistry. 1995 Jan 17;34(2):405-14. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/7819232 7819232] | ||
[[Category: Aspartate transaminase]] | [[Category: Aspartate transaminase]] | ||
[[Category: Gallus gallus]] | [[Category: Gallus gallus]] | ||
| Line 19: | Line 28: | ||
[[Category: transferase(aminotransferase)]] | [[Category: transferase(aminotransferase)]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Mar 20 09:58:46 2008'' | ||
Revision as of 10:58, 20 March 2008
| |||||||
| , resolution 2.3Å | |||||||
|---|---|---|---|---|---|---|---|
| Ligands: | |||||||
| Activity: | Aspartate transaminase, with EC number 2.6.1.1 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
STRUCTURAL BASIS FOR THE CATALYTIC ACTIVITY OF ASPARTATE AMINOTRANSFERASE K258H LACKING ITS PYRIDOXAL-5'-PHOSPHATE-BINDING LYSINE RESIDUE
OverviewOverview
Chicken mitochondrial and Escherichia coli aspartate aminotransferases K258H, in which the active site lysine residue has been exchanged for a histidine residue, retain partial catalytic competence [Ziak et al. (1993) Eur. J. Biochem. 211, 475-484]. Mutant PLP and PMP holoenzymes and the complexes of the latter (E. coli enzyme) with sulfate and 2-oxoglutarate, as well as complexes of the mitochondrial apoenzyme with N-(5'-phosphopyridoxyl)-L-aspartate or N-(5'-phosphopyridoxyl)-L-glutamate, were crystallized and analyzed by means of X-ray crystallography in order to examine how the side chain of histidine 258 can substitute as a general acid/base catalyst of the aldimine-ketimine tautomerization in enzymic transamination. The structures have been solved and refined at resolutions between 2.1 and 2.8 A. Both the closed and the open conformations, identical to those of the wild-type enzyme, were observed, indicating that the mutant enzymes of both species exhibit the same conformational flexibility as the wild-type enzymes, although in AspAT K258H the equilibrium is somewhat shifted toward the open conformation. The replacement of the active site K258 by a histidine residue resulted only in local structural adaptations necessary to accommodate the imidazole ring. The catalytic competence of the mutant enzyme, which in the forward half-reaction is 0.1% of that of the wild-type enzyme, suggests that the imidazole group is involved in the aldimine-ketimine tautomerization. However, the imidazole ring of H258 is too far away from C alpha and C4' of the coenzyme-substrate adduct for direct proton transfer, suggesting that the 1,3-prototropic shift is mediated by a water molecule. Although there is enough space for a water molecule in this area, it has not been detected. Dynamic fluctuations of the protein matrix might transiently open a channel, giving a water molecule fleeting access to the active site.
About this StructureAbout this Structure
1AKC is a Single protein structure of sequence from Gallus gallus. Full crystallographic information is available from OCA.
ReferenceReference
Structural basis for the catalytic activity of aspartate aminotransferase K258H lacking the pyridoxal 5'-phosphate-binding lysine residue., Malashkevich VN, Jager J, Ziak M, Sauder U, Gehring H, Christen P, Jansonius JN, Biochemistry. 1995 Jan 17;34(2):405-14. PMID:7819232
Page seeded by OCA on Thu Mar 20 09:58:46 2008