PDBsum entry: 1ox5

Transferase, lyase

PDB id: 1ox5

Contents

Protein chains

532 a.a. *

Ligands

1PR ×2

Metals

_NI

Waters ×196

* Residue conservation analysis

PDB id:

1ox5

Name:

Transferase, lyase

Title:

Towards understanding the mechanism of the complex cyclization reaction catalyzed by imidazole glycerophosphate synthase

Structure:

Imidazole glycerol phosphate synthase hishf. Chain: a, b. Fragment: amidotransferase and cyclase domains. Synonym: histidine biosynthesis bifunctional amidotransferase. Igp synthase. Imgp synthase. Igps. Glutamine amidotransferase:cyclase. Engineered: yes. Mutation: yes

Source:

Saccharomyces cerevisiae. Baker's yeast. Organism_taxid: 4932. Gene: his7. Expressed in: escherichia coli. Expression_system_taxid: 562

Resolution:

2.50Å R-factor: 0.223 R-free: 0.246

Authors:

B.N.Chaudhuri,J.L.Smith

Key ref:

B.N.Chaudhuri et al. (2003). Toward understanding the mechanism of the complex cyclization reaction catalyzed by imidazole glycerolphosphate synthase: crystal structures of a ternary complex and the free enzyme. Biochemistry, 42, 7003-7012. PubMed id: 12795595 DOI: 10.1021/bi034320h

Date:

01-Apr-03 Release date: 17-Jun-03

Protein chains

P33734  (HIS5_YEAST) -  Imidazole glycerol phosphate synthase hisHF

Seq: 552 a.a.

Struc: 532 a.a.*

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

 Gene Ontology (GO) functional annotation 

• Cellular component: intracellular (2 terms)
• Biological process: metabolic process (6 terms)
• Biochemical function: catalytic activity (5 terms)

DOI no: 10.1021/bi034320h

Biochemistry 42:7003-7012 (2003)

PubMed id: 12795595

Toward understanding the mechanism of the complex cyclization reaction catalyzed by imidazole glycerolphosphate synthase: crystal structures of a ternary complex and the free enzyme.

B.N.Chaudhuri, S.C.Lange, R.S.Myers, V.J.Davisson, J.L.Smith.

ABSTRACT

Imidazole glycerol phosphate synthase catalyzes formation of the imidazole ring in histidine biosynthesis. The enzyme is also a glutamine amidotransferase, which produces ammonia in a glutaminase active site and channels it through a 30-A internal tunnel to a cyclase active site. Glutaminase activity is impaired in the resting enzyme, and stimulated by substrate binding in the cyclase active site. The signaling mechanism was investigated in the crystal structure of a ternary complex in which the glutaminase active site was inactivated by a glutamine analogue and the unstable cyclase substrate was cryo-trapped in the active site. The orientation of N(1)-(5'-phosphoribulosyl)-formimino-5-aminoimidazole-4-carboxamide ribonucleotide in the cyclase active site implicates one side of the cyclase domain in signaling to the glutaminase domain. This side of the cyclase domain contains the interdomain hinge. Two interdomain hydrogen bonds, which do not exist in more open forms of the enzyme, are proposed as molecular signals. One hydrogen bond connects the cyclase domain to the substrate analogue in the glutaminase active site. The second hydrogen bond connects to a peptide that forms an oxyanion hole for stabilization of transient negative charge during glutamine hydrolysis. Peptide rearrangement induced by a fully closed domain interface is proposed to activate the glutaminase by unblocking the oxyanion hole. This interpretation is consistent with biochemical results [Myers, R. S., and with structures of the free enzyme and a binary complex with a second glutamine analogue.