A three-dimensional model of SIVmac251 IN catalytic core domain colored by amino acid similarity with wild-type HIV-1 IN. The enzyme is coloured by sequence similarity with its HIV-1 orthologue [PDB:1BL3]. The level of similarity was calculated by the Swiss PDB Viewer (SPDBV) software. The colour scale is that adopted by SPDBV. Similarity is maximal at the level of the INSTI/cellular DNA binding site (indicated by a semi-transparent grey circle), as calculated by some of us in previous works . Image obtained using PyMOL .