title: Structural studies of postentry restriction factors reveal antiparallel dimers that enable avid binding to the HIV-1 capsid lattice.
abstract: Restriction factors (RFs) form important components of host defenses to retroviral infection. The Fv1, Trim5α, and TrimCyp RFs contain N-terminal dimerization and C-terminal specificity domains that target assembled retroviral capsid (CA) proteins enclosing the viral core. However, the molecular detail of the interaction between RFs and their CA targets is unknown. Therefore, we have determined the crystal structure of the B-box and coiled-coil (BCC) region from Trim5α and used small-angle X-ray scattering to examine the solution structure of Trim5α BCC, the dimerization domain of Fv1 (Fv1Ntd), and the hybrid restriction factor Fv1Cyp comprising Fv1NtD fused to the HIV-1 binding protein Cyclophilin A (CypA). These data reveal that coiled-coil regions of Fv1 and Trim5α form extended antiparallel dimers. In Fv1Cyp, two CypA moieties are located at opposing ends, creating a molecule with a dumbbell appearance. In Trim5α, the B-boxes are located at either end of the coiled-coil, held in place by interactions with a helical motif from the L2 region of the opposing monomer. A comparative analysis of Fv1Cyp and CypA binding to a preformed HIV-1 CA lattice reveals how RF dimerization enhances the affinity of interaction through avidity effects. We conclude that the antiparallel organization of the NtD regions of Fv1 and Trim5α dimers correctly positions C-terminal specificity and N-terminal effector domains and facilitates stable binding to adjacent CA hexamers in viral cores.
authors: Divisions of Molecular Structure,School of Biological Sciences, University of Auckland, Auckland, New Zealand; and d.goldstone@auckland.ac.nz itaylor@nimr.mrc.ac.uk.
authors: David C
authors: DC
authors: Goldstone
authors: Divisions of Molecular Structure.
authors: Philip A
authors: PA
authors: Walker
authors: Physical Biochemistry, and.
authors: Lesley J
authors: LJ
authors: Calder
authors: Divisions of Molecular Structure.
authors: Peter J
authors: PJ
authors: Coombs
authors: School of Biological Sciences, University of Auckland, Auckland, New Zealand; and.
authors: Joshua
authors: J
authors: Kirkpatrick
authors: Divisions of Molecular Structure.
authors: Neil J
authors: NJ
authors: Ball
authors: Virology, National Institute for Medical Research, London NW7 1AA, United Kingdom;
authors: Laura
authors: L
authors: Hilditch
authors: Virology, National Institute for Medical Research, London NW7 1AA, United Kingdom;
authors: Melvyn W
authors: MW
authors: Yap
authors: Physical Biochemistry, and.
authors: Peter B
authors: PB
authors: Rosenthal
authors: Virology, National Institute for Medical Research, London NW7 1AA, United Kingdom;Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom.
authors: Jonathan P
authors: JP
authors: Stoye
authors: Divisions of Molecular Structure, d.goldstone@auckland.ac.nz itaylor@nimr.mrc.ac.uk.
authors: Ian A
authors: IA
authors: Taylor
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017122:Bacteriophage T4 / Q000201:enzymology; D001483:Base Sequence; D002213:Capsid / Q000378:metabolism*; D002850:Chromatography, Gel; D003460:Crystallization; D019281:Dimerization; D004926:Escherichia coli; D015497:HIV-1 / Q000378:metabolism*; D016014:Linear Models; D008253:Macaca mulatta; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009113:Muramidase / Q000737:chemistry*; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics; D053838:Scattering, Small Angle; D017422:Sequence Analysis, DNA; D020349:Surface Plasmon Resonance; D044767:Ubiquitin-Protein Ligases; D053586:Virus Internalization; D014961:X-Ray Diffraction
chemical_list: C103189:Fv1 protein, mouse; D011506:Proteins; D011993:Recombinant Fusion Proteins; C482587:TRIM5(alpha) protein, rhesus monkey; D044767:Ubiquitin-Protein Ligases; D009113:Muramidase
keywords: MLV; SAXS; X-ray crystallography; retrovirus