Genetic Organization of a 50-kb Gene Cluster Isolated from Streptomyces kanamyceticus for Kanamycin Biosynthesis and Characterization of Kanamycin Acetyltransferase

Genetic Organization of a 50-kb Gene Cluster Isolated from Streptomyces kanamyceticus for Kanamycin Biosynthesis and Characterization of Kanamycin Acetyltransferase

A 50-kb chromosome DNA region was isolated from Streptomyces kanamyceticus by screening the fosmid genomic library, using the 16S rRNA methylase gene (kmr) as a probe. Sequence analysis of this region revealed 42 putative open reading frames (ORFs), which included biosynthetic genes such as genes responsible for 2-deoxystreptamine (2­DOS) biosynthesis as well as genes for resistance and regulatory function. Also, the kanamycin acetyltransferase gene (kac) was characterized by in vitro enzyme assay, which conferred E. coli BL21 (DE3) with 10, 50, and 80-times higher resistance to kanamycin A, tobramycin, and amikacin, respectively, than the control strain had, thus strongly indicating that the isolated gene cluster is very likely involved in kanamycin biosynthesis. This work provides a solid basis for further elucidation of the kanamycin biosynthesis pathway as well as the productivity improvement and construction of new hybrid antibiotics.