kanR

KanR is a commonly used selectable marker in molecular biology that provides resistance to the antibiotic kanamycin. In plasmids and transposons, KanR is encoded by a gene that enables host cells to survive exposure to kanamycin, allowing researchers to identify cells that have taken up the recombinant construct.

Most KanR genes encode an aminoglycoside-modifying enzyme, typically an aminoglycoside phosphotransferase such as APH(3')-II, or, in some constructs, a neomycin phosphotransferase. These enzymes inactivate kanamycin by phosphorylation, reducing the antibiotic’s ability to inhibit protein synthesis. The resistance is expressed when the gene is transcribed and translated under the control of an appropriate promoter in the bacterial host.

KanR is widely used as a selectable marker in bacterial cloning, particularly in Escherichia coli, and is also used in some eukaryotic systems with suitable hosts and expression elements. Selection involves plating transformed cells on growth media containing kanamycin at concentrations that inhibit non-transformed cells; typical concentrations for E. coli range from tens to a few hundred micrograms per milliliter depending on strain and plasmid copy number.

Different plasmids may use different KanR variants or promoters; some vectors use KanR together with other markers such as AmpR or CmR depending on the experimental needs. Because KanR confers antibiotic resistance, its use is subject to biosafety and regulatory guidelines to prevent dissemination of resistance genes.

See also: antibiotic resistance markers, selectable markers, aph genes, neomycin resistance, kanamycin.