Structural insights into the diazabicyclooctane (DBO) inhibition: Avibactam inactivation of prevalent extended-spectrum beta-lactamases (ESBL) (Conferencia Semiplenaria))

BÁRBARA GHIGLIONE; GABRIEL GUTKIND; SEBASTIÁN KLINKE; MELINA RUGGIERO; FLORENCIA BRUNETTI; ROBERT A. BONOMO; PABLO POWER; MARIA M. RODRÍGUEZ; YOSHIKAZU ISHII

Bahía Blanca

Congreso; XIII Reunión Anual de la Asociación Argentina de Cristalografía (AACr); 2017

Asociación Argentina de Cristalografía (AACr)

AVI is a reversible diazabicyclo[3.2.1]octanone, DBO, beta-lactamase inhibitor (BLI) that inactivates class A and C beta-lactamases. As the diversity of class A and C beta-lactamases is ever increasing, understanding the mechanistic and structural basis of inhibition by AVI can give insight into future resistance development. PER-2 beta-lactamase possesses unique structural features that enlarge the active site entrance by 2-fold vs. other class A beta-lactamases. Uniquely, an H-bonding (HB) network is also observed and may play a role in their different catalytic profiles. CTX-M-151 possesses 70% amino acid identity with closest CTX-M beta-lactamases. It demonstrates a higher catalytic efficiency towards cefepime, and 5X higher KI value of clavulanic acid, compared to CTX-M-9. Our goal was to provide insights into the ability of AVI to inhibit these singular beta-lactamases and to probe the mechanism of inhibition. The structure of CTX-M-151 in complex with AVI was refined at 1.3 A. Here, AVI adopted an equivalent position in the active site of CTX-M-151 as CTX-M-15, showing the carbonyl oxygen pointing towards the oxyanion hole and close FIB interactions with K73, N104, 5130, N132, T235, and 5237. The structure of PER-2/AVI complex refined at 2.4 A showed 4 monomers/asu. In contrast, we observed that the W105 side chain moved >5 A towards the active site upon binding of AVI; this is accompanied by an approx 4-A shift of T104 side chain that forms a new HB with H170. This residue, belonging to the inverted omega-loop, lies in a favored position by FIB with T104, N132 and E166 carbonyl revealed. AVI also formed the same other HB interactions as CTX-M-151. Insights into the structures of both PER-2 and CTX-M-151 in complex with AVI reveal distinctive interactions of AVI with residues in the active site of these two ESBLs. In the case of PER-2, the significant rearrangements and movement of residues such as W105 and T104 upon binding of AVI is unprecedented compared to other class A enzymes.