Integrase is an enzyme that splices viral DNA; it is well known in studies of HIV. Four copies of integrase will attach to viral DNA and create a larger structure called an  intasome. This structure has 2 subunits toward the middle which will provide the active site where  the DNA is cut and attached together. This is important because it allows the viral genome to become part of the cell, furthermore propagating the virus. In the pyMOL image attached, you can see this active site mentioned.