CRYSTAL STRUCTURES OF THE CATALYTIC DOMAIN OF HIV-1 INTEGRASE FREE AND COMPLEXED WITH ITS METAL COFACTOR : HIGH SIMILARITY OF THE ACTIVE SITE WITH OTHER VIRAL INTEGRASES

Sébastien Maignan, Jean-Pierre Guilloteau, Qing Zhou-Liu, Christine Clément-Mella & Vincent Mikol*

Rhône-Poulenc Rorer; 13, Quai J. Guesde, F-94403 Vitry/Seine, France.

Keywords : integrase, HIV-1, drug design, crystallisation, cacodylate

HIV integrase is the enzyme responsible for insertion of a DNA copy of the viral genome into host DNA, an essential step in the replication cycle of HIV. HIV-1 integrase comprises three functional and structural domains : a N-terminal zinc binding domain, a catalytic core domain and a C-terminal DNA binding domain. The catalytic core domain with the F185H mutation has been crystallized without sodium cacodylate in a new crystal form free and complexed with the catalytic metal Mg²⁺. The structures have been determined and refined to about 2.2 A. Unlike the previously reported structures, the three active site carboxylate residues (D,D-35-E motif) are well ordered and both aspartates delineate a proper metal binding site. Comparison of the active binding site of this domain with that of other members from the polynucleotidyl transferases superfamily shows a high similarity. HIV-1 encodes three enzymes that are assembled into the viral particle and catalyze essential steps in the infectious cycle: the protease, the reverse transcriptase and the integrase. Structure based drug design approaches have been successfully applied for the first two of them. It has contributed to the developpment of drugs which have greatly improved the outcome of patients infected with AIDS. For the HIV-1 IN molecule structures of ligand/protein complexes have not yet emerged presumably because the only crystal form available so far represented a distorted picture of the active site conformation. The new crystal form described here should be suitable for the development of a structure aided drug design approach.