Nucleotide sequence of the chloramphenicol acetyltransferase gene of Streptomyces acrimycini

The nucleotide sequence of a gene ( cat) encoding chloramphenicol acetyltransferase (CAT) in Streptomyces acrimycini was determined. The predicted amino acid sequence demonstrates extensive homology with those of CATs isolated from Gram-negative Enterobacteria, notably with the type III variant encoded by the IncK plasmid R387. Transcript mapping indicates a single cat mRNA with a 5′ end coinciding with the AUG codon used for translational initiation m vivo. We also determined the extent of a spontaneous deletion in the 5′-noncoding DNA, which occurs when the gene is cloned in the BamHI site ofpBR322 in a specific orientation and which results in constitutive cat expression in Escherichia coli from the tet promoter.