Phylogeny of LCR-1 and OXA-5 with class A and class D beta-lactamases

The nucleotide sequences of blaLCR-1 and blaOXA-5 beta-lactamase genes have been determined. Polypeptide products of 260 and 267 amino acids with estimated molecular masses of 27 120 Da and 27,387 Da were obtained for the mature form of LCR-1 and OXA-5 proteins. A progressive alignment was used to evaluate the extent of identity between LCR-1 and OXA-5 with 29 other beta-lactamase amino acid sequences. The data showed that both belong to class D. We identified amino acids conserved in 24 positions for class A beta-lactamases and in 28 positions for five class D enzymes. The structural similarities between class A and class D beta-lactamases are more extensive than indicated by earlier biochemical studies with overall 16% identity between both classes. From the alignment, dendograms were constructed with a distance-matrix and parsimony methods which defined three major groups of proteins subdivided into clusters giving insight on beta-lactamase phylogeny and evolution.