PDBsum entry 1szu

Transferase

PDB id: 1szu

Contents

Protein chains

425 a.a. *

Ligands

SO4 ×11

EDO ×14

PLP ×4

PMP ×4

Waters ×955

* Residue conservation analysis

PDB id:

1szu

Name:

Transferase

Title:

The structure of gamma-aminobutyrate aminotransferase mutant: v241a

Structure:

4-aminobutyrate aminotransferase. Chain: a, b, c, d. Synonym: gamma-amino-n-butyrate transaminase, gaba transaminase, glutamate:succinic semialdehyde transaminase, gaba aminotransferase, gaba-at. Engineered: yes. Mutation: yes

Source:

Escherichia coli. Organism_taxid: 562. Gene: gabt, b2662. Expressed in: escherichia coli. Expression_system_taxid: 562

Biol. unit:

Tetramer (from PQS)

Resolution:

2.52Å R-factor: 0.154 R-free: 0.202

Authors:

W.Liu,P.E.Peterson,J.A.Langston,X.Jin,X.Zhou,A.J.Fisher,M.D.Toney

Key ref:

W.Liu et al. (2005). Kinetic and crystallographic analysis of active site mutants of Escherichia coli gamma-aminobutyrate aminotransferase. Biochemistry, 44, 2982-2992. PubMed id: 15723541 DOI: 10.1021/bi048657a

Date:

06-Apr-04 Release date: 01-Mar-05

Protein chains

P22256  (GABT_ECOLI) -  4-aminobutyrate aminotransferase GabT from Escherichia coli (strain K12)

Seq: 426 a.a.

Struc: 425 a.a.*

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

Enzyme reactions

• Enzyme class 1: E.C.2.6.1.19 - 4-aminobutyrate--2-oxoglutarate transaminase.
• Reaction: 4-aminobutanoate + 2-oxoglutarate = succinate semialdehyde + L-glutamate

4-aminobutanoate + 2-oxoglutarate (Bound ligand (Het Group name = EDO) matches with 40.00% similarity) = succinate semialdehyde + L-glutamate

• Cofactor: Pyridoxal 5'-phosphate

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

• Enzyme class 2: E.C.2.6.1.48 - 5-aminovalerate transaminase.
• Reaction: 5-aminopentanoate + 2-oxoglutarate = 5-oxopentanoate + L-glutamate

5-aminopentanoate + 2-oxoglutarate (Bound ligand (Het Group name = EDO) matches with 40.00% similarity) = 5-oxopentanoate + L-glutamate

• Cofactor: Pyridoxal 5'-phosphate

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

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

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

reference

DOI no: 10.1021/bi048657a

Biochemistry 44:2982-2992 (2005)

PubMed id: 15723541

Kinetic and crystallographic analysis of active site mutants of Escherichia coli gamma-aminobutyrate aminotransferase.

W.Liu, P.E.Peterson, J.A.Langston, X.Jin, X.Zhou, A.J.Fisher, M.D.Toney.

ABSTRACT

The E. coli isozyme of gamma-aminobutyrate aminotransferase (GABA-AT) is a tetrameric pyridoxal phosphate-dependent enzyme that catalyzes transamination between primary amines and alpha-keto acids. The roles of the active site residues V241, E211, and I50 in the GABA-AT mechanism have been probed by site-directed mutagenesis. The beta-branched side chain of V241 facilitates formation of external aldimine intermediates with primary amine substrates, while E211 provides charge compensation of R398 selectively in the primary amine half-reaction and I50 forms a hydrophobic lid at the top of the substrate binding site. The structures of the I50Q, V241A, and E211S mutants were solved by X-ray crystallography to resolutions of 2.1, 2.5, and 2.52 A, respectively. The structure of GABA-AT is similar in overall fold and active site structure to that of dialkylglycine decarboxylase, which catalyzes both transamination and decarboxylation half-reactions in its normal catalytic cycle. Therefore, an attempt was made to convert GABA-AT into a decarboxylation-dependent aminotransferase similar to dialkylglycine decarboxylase by systematic mutation of E. coli GABA-AT active site residues. Two of the twelve mutants presented, E211S/I50G/C77K and E211S/I50H/V80D, have approximately 10-fold higher decarboxylation activities than the wild-type enzyme, and the E211S/I50H/V80D has formally changed the reaction specificity to that of a decarboxylase.