title: A crystal structure of the catalytic core domain of an avian sarcoma and leukemia virus integrase suggests an alternate dimeric assembly.
abstract: Integrase (IN) is an important therapeutic target in the search for anti-Human Immunodeficiency Virus (HIV) inhibitors. This enzyme is composed of three domains and is hard to crystallize in its full form. First structural results on IN were obtained on the catalytic core domain (CCD) of the avian Rous and Sarcoma Virus strain Schmidt-Ruppin A (RSV-A) and on the CCD of HIV-1 IN. A ribonuclease-H like motif was revealed as well as a dimeric interface stabilized by two pairs of α-helices (α1/α5, α5/α1). These structural features have been validated in other structures of IN CCDs. We have determined the crystal structure of the Rous-associated virus type-1 (RAV-1) IN CCD to 1.8 Å resolution. RAV-1 IN shows a standard activity for integration and its CCD differs in sequence from that of RSV-A by a single accessible residue in position 182 (substitution A182T). Surprisingly, the CCD of RAV-1 IN associates itself with an unexpected dimeric interface characterized by three pairs of α-helices (α3/α5, α1/α1, α5/α3). A182 is not involved in this novel interface, which results from a rigid body rearrangement of the protein at its α1, α3, α5 surface. A new basic groove that is suitable for single-stranded nucleic acid binding is observed at the surface of the dimer. We have subsequently determined the structure of the mutant A182T of RAV-1 IN CCD and obtained a RSV-A IN CCD-like structure with two pairs of buried α-helices at the interface. Our results suggest that the CCD of avian INs can dimerize in more than one state. Such flexibility can further explain the multifunctionality of retroviral INs, which beside integration of dsDNA are implicated in different steps of the retroviral cycle in presence of viral ssRNA.
authors.affiliation: Biocristallographie et Biologie Structurale des Cibles Thérapeutiques, Institut de Biologie et Chimie des Protéines, UMR 5086 BMSSI-Centre National de la Recherche Scientifique/Université de Lyon, Lyon, France.
authors.forename: Allison
authors.initials: A
authors.lastname: Ballandras
authors.forename: Karen
authors.initials: K
authors.lastname: Moreau
authors.forename: Xavier
authors.initials: X
authors.lastname: Robert
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Confort
authors.forename: Romain
authors.initials: R
authors.lastname: Merceron
authors.forename: Richard
authors.initials: R
authors.lastname: Haser
authors.forename: Corinne
authors.initials: C
authors.lastname: Ronfort
authors.forename: Patrice
authors.initials: P
authors.lastname: Gouet
mesh_terms: D001355:Alpharetrovirus / Q000201:enzymology*; D000595:Amino Acid Sequence; D001354:Avian Leukosis Virus / Q000201:enzymology; D001358:Avian Sarcoma Viruses / Q000201:enzymology; D001665:Binding Sites / Q000235:genetics; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019426:Integrases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D053838:Scattering, Small Angle; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014961:X-Ray Diffraction
chemical_list: D014764:Viral Proteins; D019426:Integrases