Nucleotide sequence and expression of a gentamicin resistance gene isolated from the R plasmid in Serratia marcescens

The 1.0 kb fragment carrying a gentamicin resistance determinant was subcloned from the R plasmid in clinical isolates of Serratia marcescens and its nucleotide sequence was determined. It contains an open reading frame composed of 858 nucleotides, which shows 97% homology to the aacC2 gene in nucleotide sequence. Minicells carrying the 1.0 kb insert DNA on the plasmids produced a 30 kd protein that was consistent with the expected size of the deduced amino acid sequence from the open reading frame. A search for the promoter revealed a putative promoter of which the -35 region was provided by the right end of Tn3, suggesting that the expression of the gentamicin resistance gene is dependent on the Tn3 sequence.