PDBsum entry 2a1h

Transferase

PDB id: 2a1h

Contents

Protein chain

363 a.a. *

Ligands

PLP ×2

GBN ×2

ACY

Waters ×341

* Residue conservation analysis

PDB id:

2a1h

Name:

Transferase

Title:

X-ray crystal structure of human mitochondrial branched chain aminotransferase (bcatm) complexed with gabapentin

Structure:

Branched chain aminotransferase. Chain: a, b. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: mitochondrial bcat. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Biol. unit:

Dimer (from PQS)

Resolution:

1.80Å R-factor: 0.208 R-free: 0.232

Authors:

M.Goto,I.Miyahara,K.Hirotsu,M.Conway,N.Yennawar,M.M.Islam,S.M.Hutson

Key ref:

M.Goto et al. (2005). Structural determinants for branched-chain aminotransferase isozyme-specific inhibition by the anticonvulsant drug gabapentin. J Biol Chem, 280, 37246-37256. PubMed id: 16141215 DOI: 10.1074/jbc.M506486200

Date:

20-Jun-05 Release date: 06-Sep-05

Protein chains

O15382  (BCAT2_HUMAN) -  Branched-chain-amino-acid aminotransferase, mitochondrial from Homo sapiens

Seq: 392 a.a.

Struc: 363 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.2.6.1.42 - branched-chain-amino-acid transaminase.
• Pathway: Leucine Biosynthesis
• Reaction: L-leucine + 2-oxoglutarate = 4-methyl-2-oxopentanoate + L-glutamate

L-leucine + 2-oxoglutarate (Bound ligand (Het Group name = GBN) matches with 46.67% similarity) = 4-methyl-2-oxopentanoate + L-glutamate

• Cofactor: Pyridoxal 5'-phosphate

Pyridoxal 5'-phosphate (Bound ligand (Het Group name = PLP) matches with 93.75% similarity)

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1074/jbc.M506486200

J Biol Chem 280:37246-37256 (2005)

PubMed id: 16141215

Structural determinants for branched-chain aminotransferase isozyme-specific inhibition by the anticonvulsant drug gabapentin.

M.Goto, I.Miyahara, K.Hirotsu, M.Conway, N.Yennawar, M.M.Islam, S.M.Hutson.

ABSTRACT

This study presents the first three-dimensional structures of human cytosolic branched-chain aminotransferase (hBCATc) isozyme complexed with the neuroactive drug gabapentin, the hBCATc Michaelis complex with the substrate analog, 4-methylvalerate, and the mitochondrial isozyme (hBCATm) complexed with gabapentin. The branched-chain aminotransferases (BCAT) reversibly catalyze transamination of the essential branched-chain amino acids (leucine, isoleucine, valine) to alpha-ketoglutarate to form the respective branched-chain alpha-keto acids and glutamate. The cytosolic isozyme is the predominant BCAT found in the nervous system, and only hBCATc is inhibited by gabapentin. Pre-steady state kinetics show that 1.3 mm gabapentin can completely inhibit the binding of leucine to reduced hBCATc, whereas 65.4 mm gabapentin is required to inhibit leucine binding to hBCATm. Structural analysis shows that the bulky gabapentin is enclosed in the active-site cavity by the shift of a flexible loop that enlarges the active-site cavity. The specificity of gabapentin for the cytosolic isozyme is ascribed at least in part to the location of the interdomain loop and the relative orientation between the small and large domain which is different from these relationships in the mitochondrial isozyme. Both isozymes contain a CXXC center and form a disulfide bond under oxidizing conditions. The structure of reduced hBCATc was obtained by soaking the oxidized hBCATc crystals with dithiothreitol. The close similarity in active-site structures between cytosolic enzyme complexes in the oxidized and reduced states is consistent with the small effect of oxidation on pre-steady state kinetics of the hBCATc first half-reaction. However, these kinetic data do not explain the inactivation of hBCATm by oxidation of the CXXC center. The structural data suggest that there is a larger effect of oxidation on the interdomain loop and residues surrounding the CXXC center in hBCATm than in hBCATc.

Selected figure(s)

Figure 4.
FIGURE 4. Schematic diagram showing hydrogen-bond and salt-bridge interactions of the active-site residues. Putative interactions are shown by dotted lines if the acceptor and donor are less than 3.5 Å apart. The hydrogen bonds associated with the phosphate group of PLP are omitted for clarity. A, hBCATc-ox complexed with gabapentin. B, hBCATc-ox complexed with 4MeVA.

Figure 6.
FIGURE 6. Stereo diagram of the superimposed active sites of hBCATc-ox·gabapentin and hBCATc·gabapentin. The residues and gabapentin, which represent hBCATc-ox·gabapentin and hBCATc·gabapentin, are shown in brown and deep blue, respectively.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2005, 280, 37246-37256) copyright 2005.

Figures were selected by an automated process.