PDBsum entry 3kos

Transcription

PDB id: 3kos

Contents

Protein chain

200 a.a. *

Ligands

MES ×2

GOL ×7

Waters ×175

* Residue conservation analysis

PDB id:

3kos

Name:

Transcription

Title:

Structure of the ampr effector binding domain from citrobacter freundii

Structure:

Hth-type transcriptional activator ampr. Chain: a. Fragment: unp residues 83-291, effector binding domain. Engineered: yes

Source:

Citrobacter freundii. Organism_taxid: 546. Gene: ampr. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.83Å R-factor: 0.174 R-free: 0.202

Authors:

B.L.Mark,M.D.Balcewich

Key ref:

M.D.Balcewich et al. (2010). Crystal structure of the AmpR effector binding domain provides insight into the molecular regulation of inducible ampc beta-lactamase. J Mol Biol, 400, 998-1010. PubMed id: 20594961

Date:

13-Nov-09 Release date: 26-May-10

Protein chain

P12529  (AMPR_CITFR) -  HTH-type transcriptional activator AmpR from Citrobacter freundii

Seq: 291 a.a.

Struc: 200 a.a.*

* PDB and UniProt seqs differ at 3 residue positions (black crosses)

J Mol Biol 400:998-1010 (2010)

PubMed id: 20594961

Crystal structure of the AmpR effector binding domain provides insight into the molecular regulation of inducible ampc beta-lactamase.

M.D.Balcewich, T.M.Reeve, E.A.Orlikow, L.J.Donald, D.J.Vocadlo, B.L.Mark.

ABSTRACT

Hyperproduction of AmpC beta-lactamase (AmpC) is a formidable mechanism of resistance to penicillins and cephalosporins in Gram-negative bacteria such as Pseudomonas aeruginosa and Enterobacteriaceae. AmpC expression is regulated by the LysR-type transcriptional regulator AmpR. ampR and ampC genes form a divergent operon with overlapping promoters to which AmpR binds and regulates the transcription of both genes. AmpR induces ampC by binding to one member of the family of 1,6-anhydro-N-acetylmuramyl peptides, which are cytosolic catabolites of peptidoglycan that accumulate during beta-lactam challenge. To gain structural insights into AmpR regulation, we determined the crystal structure of the effector binding domain (EBD) of AmpR from Citrobacter freundii up to 1.83 A resolution. The AmpR EBD is dimeric and each monomer comprises two subdomains that adopt alpha/beta Rossmann-like folds. Located between the monomer subdomains is a pocket that was found to bind the crystallization buffer molecule 2-(N-morpholino)ethanesulfonic acid. The pocket, together with a groove along the surface of subdomain I, forms a putative effector binding site into which a molecule of 1,6-anhydro-N-acetylmuramyl pentapeptide could be modeled. Amino acid substitutions at the base of the interdomain pocket either were found to render AmpR incapable of inducing ampC (Thr103Val, Ser221Ala and Tyr264Phe) or resulted in constitutive ampC expression (Gly102Glu). While the substitutions that prevented ampC induction did not alter the overall AmpR EBD structure, circular dichroism spectroscopy revealed that the nonconservative Gly102Glu mutation affected EBD secondary structure, confirming previous work suggesting that Gly102Glu induces a conformational change to result in constitutive AmpC production.