PDBsum entry: 1gex

Transferase

PDB id: 1gex

Contents

Protein chain

339 a.a. *

Ligands

PLP-HSA

Waters ×120

* Residue conservation analysis

PDB id:

1gex

Name:

Transferase

Title:

Crystal structure of histidinol-phosphate aminotransferasE C with histidinol-phosphate

Structure:

Histidinol-phosphate aminotransferase. Chain: a. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 562. Gene: hisc. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PDB file)

Resolution:

2.20Å R-factor: 0.191 R-free: 0.261

Authors:

K.Haruyama,T.Nakai,I.Miyahara,K.Hirotsu,H.Mizuguchi,H.Hayash H.Kagamiyama

Key ref:

K.Haruyama et al. (2001). Structures of Escherichia coli histidinol-phosphate aminotransferase and its complexes with histidinol-phosphate and N-(5'-phosphopyridoxyl)-L-glutamate: double substrate recognition of the enzyme. Biochemistry, 40, 4633-4644. PubMed id: 11294630 DOI: 10.1021/bi002769u

Date:

30-Nov-00 Release date: 18-Apr-01

Protein chain

P06986  (HIS8_ECOLI) -  Histidinol-phosphate aminotransferase

Seq: 356 a.a.

Struc: 339 a.a.

Enzyme reactions

• Enzyme class: E.C.2.6.1.9 - Histidinol-phosphate transaminase.
• Pathway: Histidine Biosynthesis (late stages)
• Reaction: L-histidinol phosphate + 2-oxoglutarate = 3-(imidazol-4-yl)-2-oxopropyl phosphate + L-glutamate

L-histidinol phosphate (Bound ligand (Het Group name = HSA) corresponds exactly) + 2-oxoglutarate = 3-(imidazol-4-yl)-2-oxopropyl phosphate + 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

 Gene Ontology (GO) functional annotation 

• Biological process: metabolic process (4 terms)
• Biochemical function: catalytic activity (7 terms)

reference

DOI no: 10.1021/bi002769u

Biochemistry 40:4633-4644 (2001)

PubMed id: 11294630

Structures of Escherichia coli histidinol-phosphate aminotransferase and its complexes with histidinol-phosphate and N-(5'-phosphopyridoxyl)-L-glutamate: double substrate recognition of the enzyme.

K.Haruyama, T.Nakai, I.Miyahara, K.Hirotsu, H.Mizuguchi, H.Hayashi, H.Kagamiyama.

ABSTRACT

Histidinol-phosphate aminotransferase (HspAT) is a key enzyme on the histidine biosynthetic pathway. HspAT catalyzes the transfer of the amino group of L-histidinol phosphate (Hsp) to 2-oxoglutarate to form imidazole acetol phosphate (IAP) and glutamate. Thus, HspAT recognizes two kinds of substrates, Hsp and glutamate (double substrate recognition). The crystal structures of native HspAT and its complexes with Hsp and N-(5'-phosphopyridoxyl)-L-glutamate have been solved and refined to R-factors of 19.7, 19.1, and 17.8% at 2.0, 2.2, and 2.3 A resolution, respectively. The enzyme is a homodimer, and the polypeptide chain of the subunit is folded into one arm, one small domain, and one large domain. Aspartate aminotransferases (AspATs) from many species were classified into aminotransferase subgroups Ia and Ib. The primary sequence of HspAT is less than 18% identical to those of Escherichia coli AspAT of subgroup Ia and Thermus thermophilus HB8 AspAT of subgroup Ib. The X-ray analysis of HspAT showed that the overall structure is significantly similar to that of AspAT of subgroup Ib rather than subgroup Ia, and the N-terminal region moves close to the active site like that of subgroup Ib AspAT upon binding of Hsp. The folding of the main-chain atoms in the active site is conserved between HspAT and the AspATs, and more than 40% of the active-site residues is also conserved. The eHspAT recognizes both Hsp and glutamate by utilizing essentially the same active-site folding as that of AspAT, conserving the essential residues for transamination reaction, and replacing and relocating some of the active-site residues. The binding sites for the phosphate and the alpha-carboxylate groups of the substrates are roughly located at the same position and those for the imidazole and gamma-carboxylate groups at the different positions. The mechanism for the double substrate recognition observed in eHspAT is in contrast to that in aromatic amino acid aminotransferase, where the recognition site for the side chain of the acidic amino acid is formed at the same position as that for the side chain of aromatic amino acids by large-scale rearrangements of the hydrogen bond networks.