PRIMARY STRUCTURE OF OXA-3 AND PHYLOGENY OF OXACILLIN-HYDROLYZING CLASS-D BETA-LACTAMASES

We determined the nucleotide sequence of the bla(OXA-3(pMG25)) gene fr om Pseudomonas aeruginosa. The bla structural gene encoded a protein o f 275 amino acids representing one monomer of 31,879 Da for the OXA-3 enzyme. Comparisons between the OXA-3 nucleotide and amino acid sequen ces and those of class A, B, C, and D beta-lactamases were performed. An alignment of the eight known class D beta-lactamases including OXA- 3 demonstrated the presence of conserved amino acids. In addition, con served motifs composed of identical amino acids typical of penicillin- recognizing proteins and specific class D motifs were identified. Thes e conserved motifs were considered for possible roles in the structure and function of oxacillinases. On the basis of the alignment and iden tity scores, a dendrogram was constructed. The phylogenetic data obtai ned revealed five groups of class D beta-lactamases with large evoluti onary distances between each group.