Figure 1.

Overall structure and characterization of MHV-68 vPIP. (a) Crystal structure representation of MHV-68 vPIP. vPIP forms a dimer in the asymmetric unit with space group P3₂21. The crystal structure is shown with secondary structure that includes 12 α-helices and two β-strands. The dotted lines indicate the disordered loops (L1, L2 and Ct1). The chain A helix bundle is shown in light orange and the chain B helix bundle is shown in violet. (b) SPR analysis of vPIP with PARP-1. The vPIP protein was injected at five concentrations (1.72, 0.86, 0.43, 0.21 and 0.1 µM). Dissociation data were collected for 120 s. Black lines show the actual data; the orange lines are curve fits. (c) A structural model of the dimer interface of vPIP. Residues in the dimer interface are presented as stick models. In the upper and lower panels each residue in chain A (His58, Glu61, Arg65, Lys162, Glu172, Lys244, Arg254, Asp265 and Glu266) and in chain B (His58, Glu61, Arg65, Lys162, Arg72, Glu172, Lys244, Arg254, Asp265 and Glu266) involved in hydrogen bonds and salt bridges is indicated. The interaction of residues was calculated using PISA. (d) Multi-angle light-scattering and refractive-index curves for vPIP dimerization. Light scattering (LS) is shown in blue and the differential refractive index (dRI) is shown in red. The buffer was removed and the LS and refractive index were measured and plotted against the protein sample. (e) GFP-tagged vPIP and FLAG-tagged vPIP were transfected into HEK293T cells for 48 h. The cells were harvested and subjected to co-IP assays using anti-FLAG. The results were analyzed by Western blotting.