The host crystal space group and the point defect site symmetry group being given the procedure of generation of the imperfect space group in the supercell or periodic defect model is considered. The approach developed is applied to the symmetry analysis of the possible space groups of metaldoped rutile and anatase structures in the supercell model. The results of unrestricted Hartree-Fock calculations of the V-doped rutile electronic structure (an impurity atom charge, valence states, an impurity level position in the energy gap) are given. Supercells of 36, 60, 84 atoms chosen on the base of the symmetry analysis are calculated. The convergence of the results with the supercell increasing is demonstrated.