Amino acid sequence alignment of class A β-lactamase (Bla-A) of Y. intermedia (strain C-702) with its nearest β-lactamase neighbors. The partial sequence of Bla-A of Y. frederiksenii was not included in alignment analysis because the deduced amino acid sequence was of 121 residues only. Asterisks indicate identical amino acids. The conserved motifs (70SXXK73, 130SDN132 and 234KTG236) typical of class A β-lactamases are underlined and in boldface. The motif 166EXXLN170 responsible for omega-loop formation is in boldface and italics. Arrows indicate the putative omega (Ω) loop region. The GenBank accession numbers of the β-lactamases are as follows: Y.intem _702 (Y. intermedia, ABD84039, present study),Y.ent_ 1A (AAX55643, Y. enterocolitica biovar 1A), Y.ent _1B (Y. enterocolitica 8081 biovar 1B), Y.ent _4 (CAA40357, Y. enterocolitica, Y-56 biovar 4), K.oxy, (AAA25084, K. oxytoca) and C.kos (CAA44485, C. koseri).