GENE-TRANSFER OF A PART OF A BETA-LACTAMASE GENE

Beta-Lactamase is an enzyme which catalyzes the hydrolysis of the beta -lactam ring of penicillins and cephalosporins. By similarity analysis of amino acid sequences in a database, the amino acid sequence deduce d from the nucleotide sequence of the upstream region of cytochrome c oxidase subunit II from Paracoccus denitrificans was found to have an unusually high score of homology to that of a portion of beta-lactamas es from Gram-negative bacteria. Furthermore, the nucleotide sequences corresponding only to this region had a very high score of similarity among them. The phylogenetic tree constructed on the basis of the amin o acid sequences was in accord with that constituted on the 5S rRNA's. Moreover, the molar G + C contents and the codon usage were similar t o those in their respective bacteria. It is suggested, therefore, that the nucleotide sequence in P. denitrificans was positioned by a trans fer of a part of a beta-lactamase gene formed as a result of gene dupl ication or it was formed by a deletion of the essential region of the beta-lactamase gene, although no beta-lactamase gene has been yet dete cted in P. denitrificans.