Expression and biochemical characterization of the DNA binding activity of TcA, the putative transposase of Caenorhabditis elegans transposable element Tc1.

The TcA protein is one of the proteins essential for Tc1 transposition. In order to study the biochemical parameters of Tc1 transposition mechanism, we used TcA protein overproduced in baculovirus system for DNA binding experiments. We show that, despite its relatively strong non specific affinity for DNA, TcA exhibits a better affinity for its Tc1 specific binding sites. The K0.5 is 3.8 nM for the Tc1 whereas in the same type of experiment the K0.5 is 24 nM for calf thymus DNA. The ratio value between specific and non specific DNA binding activity of the TcA protein was also exhibited by other transposases such as those of the bacteriophage Mu, Tn 10 and the Drosophila P element. This nonspecific DNA binding activity may be involved in determining sites of transposable element insertion.