Kanamycin

A member of the aminoglycoside family of antibiotics, kanamycin was first iso­lated from Streptomyces kanamyceticus in Japan in 1957. This polycation is taken into the bacterial cell through outer-membrane pores but crosses the cytoplasmic mem­brane in an energy-dependent process utilizing the membrane potential. The molecule interacts with three ribosomal proteins and with rRNA in the 30S ribosomal subunit, to prevent the transition of an initiating complex to a chain-elongating complex, and thus inhibits protein synthesis. Resistance to kanamycin is conferred by amino-phosphotransferases. Those commonly encoded by vectors are Aph (3')-I from Tn903 and Aph (3')-II from Tn,5 which transfer phosphate from ATP to the kanamycin to inactivate it (16). It is important to note that these two resistance genes have differing

DNA sequences and, thus, different restriction maps. They will not cross-hybridize under stringent conditions in Southern hybridizations.