OXA-66 structure and oligomerisation of OXA Ab enzymes.

The OXA β-lactamases are responsible for hydrolysing β-lactam antibiotics and contribute to the multidrug-resistant phenotype of several major human pathogens. The OXA Ab enzymes are intrinsic to Acinetobacter baumannii and can confer resistance to carbapenem antibiotics. Here we determined the structure of the most prevalent OXA Ab enzyme, OXA-66. The structure of OXA-66 was solved at a resolution of 2.1 Å and found to be very similar to the structure of OXA-51, the only other OXA Ab enzyme that has had its structure solved. Our data contained one molecule per asymmetric unit, and analysis of positions responsible for dimer formation in other OXA enzymes suggest that OXA-66 likely exists as a monomer.