1ohy
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4-AMINOBUTYRATE-AMINOTRANSFERASE INACTIVATED BY GAMMA-ETHYNYL GABA
OverviewOverview
Gamma-aminobutyric acid aminotransferase (GABA-AT) is a pyridoxal, 5'-phosphate-dependent enzyme responsible for the degradation of the, inhibitory neurotransmitter GABA. GABA-AT is a validated target for, antiepilepsy drugs because its selective inhibition raises GABA, concentrations in brain. The antiepilepsy drug, gamma-vinyl-GABA, (vigabatrin) has been investigated in the past by various biochemical, methods and resulted in several proposals for its mechanisms of, inactivation. In this study we solved and compared the crystal structures, of pig liver GABA-AT in its native form (to 2.3-A resolution) and in, complex with vigabatrin as well as with the close analogue, gamma-ethynyl-GABA (to 2.3 and 2.8 A, respectively). Both inactivators, form a covalent ternary adduct with the active site Lys-329 and the, pyridoxal 5'-phosphate (PLP) cofactor. The crystal structures provide, direct support for specific inactivation mechanisms proposed earlier on, the basis of radio-labeling experiments. The reactivity of GABA-AT, crystals with the two GABA analogues was also investigated by polarized, absorption microspectrophotometry. The spectral data are discussed in, relation to the proposed mechanism. Intriguingly, all three structures, revealed a [2Fe-2S] cluster of yet unknown function at the center of the, dimeric molecule in the vicinity of the PLP cofactors.
About this StructureAbout this Structure
1OHY is a Single protein structure of sequence from Sus scrofa with FE, PLP and S as ligands. Active as 4-aminobutyrate transaminase, with EC number 2.6.1.19 Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Structures of gamma-aminobutyric acid (GABA) aminotransferase, a pyridoxal 5'-phosphate, and [2Fe-2S] cluster-containing enzyme, complexed with gamma-ethynyl-GABA and with the antiepilepsy drug vigabatrin., Storici P, De Biase D, Bossa F, Bruno S, Mozzarelli A, Peneff C, Silverman RB, Schirmer T, J Biol Chem. 2004 Jan 2;279(1):363-73. Epub 2003 Oct 8. PMID:14534310
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