Nucleotide sequence of the bsr gene and N-terminal amino acid sequence of blasticidin S deaminase from blasticidin S resistant Escherichia coli TK121.

duction of BS-deaminase (aminohydrolase, EC 3.5.4.23), which converted BS to an inactive derivative. Because of the broad spectrum of activity of blasticidin S, this antibioticresistance phenotype could be useful as a selection marker in genetic manipulation of both prokaryotic and eukaryotic cells. To this end, we obtained a plasmid pBSR8 (10.5kb) that encodes BS-deaminase. We describe the nucleotide sequence of the bsr gene, the determinant of the BS resistance, and compare the derived amino acid sequence with the N-terminal sequence of the enzyme purified from a resistant transformant. Cloning experiments using host vector systems of Bacillus subtilis and Escherichia coli and analyses of the recombinant plasmids located the bsr gene in the 1.5-kb EcoKl to