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Publication Abstract from PubMed

Burkholderia cepacia complex and Burkholderia pseudomallei are opportunistic human pathogens. Resistance to beta-lactams among Burkholderia spp. is attributable to expression of beta-lactamases (e.g. PenA in B. cepacia complex and PenI in B. pseudomallei). Phylogenetic comparisons reveal that PenA and PenI are highly related. However, the analyses presented here reveal that PenA is an inhibitor-resistant carbapenemase, most similar to KPC-2 (the most clinically significant serine carbapenemase), whereas PenI is an extended spectrum beta-lactamase. PenA hydrolyzes beta-lactams with k(cat) values ranging from 0.38 +/- 0.04 to 460 +/- 46 s(-1) and possesses high k(cat)/k(inact) values of 2000, 1500, and 75 for beta-lactamase inhibitors. PenI demonstrates the highest kcat value for cefotaxime of 9.0 +/- 0.9 s(-1). Crystal structure determination of PenA and PenI reveals important differences that aid in understanding their contrasting phenotypes. Changes in the positioning of conserved catalytic residues (e.g. Lys-73, Ser-130, and Tyr-105) as well as altered anchoring and decreased occupancy of the deacylation water explain the lower k(cat) values of PenI. The crystal structure of PenA with imipenem docked into the active site suggests why this carbapenem is hydrolyzed and the important role of Arg-220, which was functionally confirmed by mutagenesis and biochemical characterization. Conversely, the conformation of Tyr-105 hindered docking of imipenem into the active site of PenI. The structural and biochemical analyses of PenA and PenI provide key insights into the hydrolytic mechanisms of beta-lactamases, which can lead to the rational design of novel agents against these pathogens.

Insights into beta-lactamases from Burkholderia species, two phylogenetically related yet distinct resistance determinants.,Papp-Wallace KM, Taracila MA, Gatta JA, Ohuchi N, Bonomo RA, Nukaga M J Biol Chem. 2013 Jun 28;288(26):19090-102. doi: 10.1074/jbc.M113.458315. Epub, 2013 May 8. PMID:23658015^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.