Organization of complex transposon Tn2610 carrying two copies of tnpA and tnpR.

Transposon Tn2610 has two elements of 3.5 kilobase pairs as inverted repeats, one set at each end. This unique terminal element contained the transposition genes tnpA and tnpR. Only the tnpA gene in the left element was functional for transposition, whereas both tnpR genes were active. Possible evolutionary relationships among class II transposable elements are proposed on the basis of the genetic and structural organization of Tn2610.