TnsA endonuclease N-terminal (IPR014833). Tn7 transposase is composed of two proteins, TnsA and TnsB. At the 5' end of the transposon, TnsA is responsible for DNA cleavage, while at the 3' end, TnsB is responsible for cleavage and ligation. TnsA's N-terminal domain mediates its catalytic effect. TnsA and gp4 proteins conserve this domain, which contains a catalytic triad of a basic and two acidic residues that form a restriction endonuclease-like active site.