Genes for gentamicin-(3)-N-acetyltransferases III and IV: I. Nucleotide sequence of the AAC(3)-IV gene and possible involvement of an IS140 element in its expression.

Genes for gentamicin-3-acetyltransferases [ACC(3)] of types III and IV have been cloned from various R-plasmids. In two R-plasmids, pWP14a (AAC(3)-III) and pWP7b [AAC(3)-IV], resistance genes have been found directly adjacent to a single copy of an IS element, IS140. Nucleotide sequence determination of the AAC(3)-IV gene from plasmid pWP7b and of part of IS140 from three different sources suggested that the -35 region of the AAC(3)-IV promoter was part of the IS element. A similarly built-up promoter was found in pWP14a. It was found also, that a hygromycin B phosphotransferase was expressed from a locus neighbouring the AAC(3)-IV gene in pWP7b which was under the control of the same promoter. In two other R-plasmids, pWP113a and pWP116a, the AAC(3)-III gene was found in different genetic environments, namely close to Tn3-like structures.