PDBsum entry 1s1m

Ligase

PDB id: 1s1m

Contents

Protein chains

534 a.a. *

Ligands

SO4 ×4

MPD ×2

Metals

_MG ×4

IOD ×16

Waters ×549

* Residue conservation analysis

PDB id:

1s1m

Name:

Ligase

Title:

Crystal structure of e. Coli ctp synthetase

Structure:

Ctp synthase. Chain: a, b. Synonym: utp--ammonia ligase, ctp synthetase. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 562. Gene: pyrg, b2780, c3345, z4095, ecs3640, sf2795, s2989. Expressed in: escherichia coli. Expression_system_taxid: 562

Biol. unit:

Dimer (from PDB file)

Resolution:

2.30Å R-factor: 0.214 R-free: 0.281

Authors:

J.A.Endrizzi,H.Kim,P.M.Anderson,E.P.Baldwin

Key ref:

J.A.Endrizzi et al. (2004). Crystal structure of Escherichia coli cytidine triphosphate synthetase, a nucleotide-regulated glutamine amidotransferase/ATP-dependent amidoligase fusion protein and homologue of anticancer and antiparasitic drug targets. Biochemistry, 43, 6447-6463. PubMed id: 15157079 DOI: 10.1021/bi0496945

Date:

06-Jan-04 Release date: 15-Jun-04

Protein chains

P0A7E5  (PYRG_ECOLI) -  CTP synthase from Escherichia coli (strain K12)

Seq: 545 a.a.

Struc: 534 a.a.

Enzyme reactions

• Enzyme class: E.C.6.3.4.2 - Ctp synthase (glutamine hydrolyzing).
• Reaction: UTP + L-glutamine + ATP + H2O = CTP + L-glutamate + ADP + phosphate + 2 H⁺

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

reference

DOI no: 10.1021/bi0496945

Biochemistry 43:6447-6463 (2004)

PubMed id: 15157079

Crystal structure of Escherichia coli cytidine triphosphate synthetase, a nucleotide-regulated glutamine amidotransferase/ATP-dependent amidoligase fusion protein and homologue of anticancer and antiparasitic drug targets.

J.A.Endrizzi, H.Kim, P.M.Anderson, E.P.Baldwin.

ABSTRACT

Cytidine triphosphate synthetases (CTPSs) produce CTP from UTP and glutamine, and regulate intracellular CTP levels through interactions with the four ribonucleotide triphosphates. We solved the 2.3-A resolution crystal structure of Escherichia coli CTPS using Hg-MAD phasing. The structure reveals a nearly symmetric 222 tetramer, in which each bifunctional monomer contains a dethiobiotin synthetase-like amidoligase N-terminal domain and a Type 1 glutamine amidotransferase C-terminal domain. For each amidoligase active site, essential ATP- and UTP-binding surfaces are contributed by three monomers, suggesting that activity requires tetramer formation, and that a nucleotide-dependent dimer-tetramer equilibrium contributes to the observed positive cooperativity. A gated channel that spans 25 A between the glutamine hydrolysis and amidoligase active sites provides a path for ammonia diffusion. The channel is accessible to solvent at the base of a cleft adjoining the glutamine hydrolysis active site, providing an entry point for exogenous ammonia. Guanine nucleotide binding sites of structurally related GTPases superimpose on this cleft, providing insights into allosteric regulation by GTP. Mutations that confer nucleoside drug resistance and release CTP inhibition map to a pocket that neighbors the UTP-binding site and can accommodate a pyrimidine ring. Its location suggests that competitive feedback inhibition is affected via a distinct product/drug binding site that overlaps the substrate triphosphate binding site. Overall, the E. coli structure provides a framework for homology modeling of other CTPSs and structure-based design of anti-CTPS therapeutics.