Tc3 is transposase with a specific DNA-binding domain which contains three alpha-helices, two of which form a helix-turn-helix motif which makes four base-specific contacts with the major groove. The N-terminus makes contacts with the minor groove. There is a base specific recognition between Tc3 and the transposon DNA. The DNA binding domain forms a dimer in which each monomer binds a separate transposon end. This implicates that the dimer has a role in synapsis and is necessary for the simultaneous cleavage of both transposon termini [1].

1: Crystal structure of the specific DNA-binding domain of Tc3 transposase of C.elegans in complex with transposon DNA. van Pouderoyen G, Ketting RF, Perrakis A, Plasterk RH, Sixma TK; EMBO J 1997;16:6044-6054. PMID:9312061