Expression of a neomycin phosphotransferase gene from Streptomyces fradiae in Escherichia coli after interplasmidic recombination.

Plasmid pIJ2 carrying the neomycin phosphotransferase gene of Streptomyces fradiae was fused to E. coli plasmid pBR325 and the hybrid molecules were introduced into E. coli K12 by transformation. The neomycin phosphotransferase gene of the hybrid plasmid was not expressed in E. coli, except after interplasmidic recombination. Physical analysis of such an in vivo recombinant plasmid revealed that the recombination brought one neomycin phosphotransferase gene to a position downstream from the tet-promoter of pBR325. Subcloning experiments indicated that this is the gene copy expressed, and that transcription is initiated at the tet-promoter of pBR325.