PDBsum entry 1k0e

Lyase

PDB id: 1k0e

Contents

Protein chains

437 a.a. *

414 a.a. *

Ligands

TRP ×2

FMT

Waters ×318

* Residue conservation analysis

PDB id:

1k0e

Name:

Lyase

Title:

The crystal structure of aminodeoxychorismate synthase from formate grown crystals

Structure:

P-aminobenzoate synthase component i. Chain: a, b. Synonym: aminodeoxychorismate synthase, adc synthase. Engineered: yes

Source:

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

Resolution:

2.00Å R-factor: 0.205 R-free: 0.315

Authors:

J.F.Parsons,P.Y.Jensen,A.S.Pachikara,A.J.Howard,E.Eisenstein, J.E.Ladner

Key ref:

J.F.Parsons et al. (2002). Structure of Escherichia coli aminodeoxychorismate synthase: architectural conservation and diversity in chorismate-utilizing enzymes. Biochemistry, 41, 2198-2208. PubMed id: 11841211 DOI: 10.1021/bi015791b

Date:

19-Sep-01 Release date: 27-Feb-02

Protein chain

P05041  (PABB_ECOLI) -  Aminodeoxychorismate synthase component 1 from Escherichia coli (strain K12)

Seq: 453 a.a.

Struc: 437 a.a.

Protein chain

P05041  (PABB_ECOLI) -  Aminodeoxychorismate synthase component 1 from Escherichia coli (strain K12)

Seq: 453 a.a.

Struc: 414 a.a.

Enzyme reactions

• Enzyme class: Chains A, B: E.C.2.6.1.85 - aminodeoxychorismate synthase.
• Reaction: chorismate + L-glutamine = 4-amino-4-deoxychorismate + L-glutamate

chorismate + L-glutamine (Bound ligand (Het Group name = TRP) matches with 56.25% similarity) = 4-amino-4-deoxychorismate + L-glutamate

• Cofactor: Mg(2+)

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

reference

DOI no: 10.1021/bi015791b

Biochemistry 41:2198-2208 (2002)

PubMed id: 11841211

Structure of Escherichia coli aminodeoxychorismate synthase: architectural conservation and diversity in chorismate-utilizing enzymes.

J.F.Parsons, P.Y.Jensen, A.S.Pachikara, A.J.Howard, E.Eisenstein, J.E.Ladner.

ABSTRACT

Aminodeoxychorismate synthase is part of a heterodimeric complex that catalyzes the two-step biosynthesis of 4-amino-4-deoxychorismate, a precursor of p-aminobenzoate and folate in microorganisms. In the first step, a glutamine amidotransferase encoded by the pabA gene generates ammonia as a substrate that, along with chorismate, is used in the second step, catalyzed by aminodeoxychorismate synthase, the product of the pabB gene. Here we report the X-ray crystal structure of Escherichia coli PabB determined in two different crystal forms, each at 2.0 A resolution. The 453-residue monomeric PabB has a complex alpha/beta fold which is similar to that seen in the structures of homologous, oligomeric TrpE subunits of several anthranilate synthases of microbial origin. A comparison of the structures of these two classes of chorismate-utilizing enzymes provides a rationale for the differences in quaternary structures seen for these enzymes, and indicates that the weak or transient association of PabB with PabA during catalysis stems at least partly from a limited interface for protein interactions. Additional analyses of the structures enabled the tentative identification of the active site of PabB, which contains a number of residues implicated from previous biochemical and genetic studies to be essential for activity. Differences in the structures determined from phosphate- and formate-grown crystals, and the location of an adventitious formate ion, suggest that conformational changes in loop regions adjacent to the active site may be needed for catalysis. A surprising finding in the structure of PabB was the presence of a tryptophan molecule deeply embedded in a binding pocket that is analogous to the regulatory site in the TrpE subunits of the anthranilate synthases. The strongly bound ligand, which cannot be dissociated without denaturation of PabB, may play a structural role in the enzyme since there is no effect of tryptophan on the enzymic synthesis of aminodeoxychorismate. Extensive sequence similarity in the tryptophan-binding pocket among several other chorismate-utilizing enzymes, including isochorismate synthase, suggests that they too may bind tryptophan for structural integrity, and corroborates early ideas on the evolution of this interesting enzyme family.