Nucleotide sequence and transcriptional start point of the kan gene encoding an aminoglycoside 3-N-acetyltransferase from Streptomyces griseus SS-1198PR

Abstract

We determined the nucleotide sequence of a 1794-bp BglII-BamHI fragment containing the kan gene (KmR) which encodes a novel aminoglycoside 3-N-acetyltransferase of Streptomyces griseus SS-1198PR. The sequence was found to contain four open reading frames (ORF) in the direction of transcription determined by low resolution S1 nuclease mapping. Except for the largest one, these ORF are unlikely to be the coding sequence of kan, because of their inability to confer kanamycin resistance. The largest ORF could encode a 30.8-kDa protein consisting of 284 amino acids (aa) with 93.3 mol% G + C in the third position of codons, and is preceded by potential ribosome-binding sites. Thus, the largest ORF was likely to represent the kan gene. The transcription start point of kan was located 84 bp upstream from the start codon. The -10 region showed similarity to the Escherichia coli consensus promoter motif, while no sequence similarity was found in the -35 region. The deduced aa sequence of kan showed 85% similarity with that of the aacC7 gene of Streptomyces rimosus forma paromomycinus [Lopez-Cabrera et al., J. Bacteriol. 171 (1989) 321-328] suggesting that these genes are derived from a common ancestral gene.