1IEL

Crystal Structure of AmpC beta-lactamase from E. coli in Complex with Ceftazidime

Summary for 1IEL

• Entry DOI: 10.2210/pdb1iel/pdb
• Related: 1C3B 1FSW 1FSY 1GA9 2BLS 3BLS
• Descriptor: beta-lactamase, PHOSPHATE ION, ACYLATED CEFTAZIDIME, ... (4 entities in total)
• Functional Keywords: cephalosporinase, beta-lactamase, serine hydrolase, hydrolase
• Biological source: Escherichia coli
• Cellular location: Periplasm: P00811
• Total number of polymer chains: 2
• Total formula weight: 80209.80

Authors

Powers, R.A.,Caselli, E.,Focia, P.J.,Prati, F.,Shoichet, B.K. (deposition date: 2001-04-10, release date: 2001-08-15, Last modification date: 2024-10-30)

Primary citation

Powers, R.A.,Caselli, E.,Focia, P.J.,Prati, F.,Shoichet, B.K.
Structures of ceftazidime and its transition-state analogue in complex with AmpC beta-lactamase: implications for resistance mutations and inhibitor design.
Biochemistry, 40:9207-9214, 2001

PubMed Abstract: Third-generation cephalosporins are widely used beta-lactam antibiotics that resist hydrolysis by beta-lactamases. Recently, mutant beta-lactamases that rapidly inactivate these drugs have emerged. To investigate why third-generation cephalosporins are relatively stable to wild-type class C beta-lactamases and how mutant enzymes might overcome this, the structures of the class C beta-lactamase AmpC in complex with the third-generation cephalosporin ceftazidime and with a transition-state analogue of ceftazidime were determined by X-ray crystallography to 2.0 and 2.3 A resolution, respectively. Comparison of the acyl-enzyme structures of ceftazidime and loracarbef, a beta-lactam substrate, reveals that the conformation of ceftazidime in the active site differs from that of substrates. Comparison of the structures of the acyl-enzyme intermediate and the transition-state analogue suggests that ceftazidime blocks formation of the tetrahedral transition state, explaining why it is an inhibitor of AmpC. Ceftazidime cannot adopt a conformation competent for catalysis due to steric clashes that would occur with conserved residues Val211 and Tyr221. The X-ray crystal structure of the mutant beta-lactamase GC1, which has improved activity against third-generation cephalosporins, suggests that a tandem tripeptide insertion in the Omega loop, which contains Val211, has caused a shift of this residue and also of Tyr221 that would allow ceftazidime and other third-generation cephalosporins to adopt a more catalytically competent conformation. These structural differences may explain the extended spectrum activity of GC1 against this class of cephalosporins. In addition, the complexed structure of the transition-state analogue inhibitor (K(i) 20 nM) with AmpC reveals potential opportunities for further inhibitor design.

PubMed: 11478888
DOI: 10.1021/bi0109358

Experimental method

X-RAY DIFFRACTION (2 Å)