Figure 4. Characterization of VP40 basic patch.
(A) Electrostatic surface potential of the VP40EΔN dimer in two orientations. The dimer interface is indicated by a dashed line and the division of the NTD and CTD is depicted by a solid black line. The attachment points of the disordered GKKG loop are indicated by stars and the loop is modeled as a broken blue line (on right). (B) Western blot of cell lysates and purified VLPs from transfected cells. The VP40E-ΔGMMGΔ, VP40E-ΔGEEGΔ and VP40E-K274E/K275E constructs express, but fail to assemble or bud VLPs (red arrows). (C) IFA demonstrates that VP40E-ΔGKKGΔ and VP40E-ΔGRRGΔ assemble and bud VLPs (yellow arrows). By contrast, VP40E-ΔGEEGΔ and VP40E-ΔGMMGΔ fail to interact with the membrane. While VP40E-K274E/K275E clearly migrates to and interacts with the cell membrane, but fails to assemble and bud VLPs. (D) EM micrographs display active VLP assembly and budding for VP40E-ΔGKKGΔ and VP40E-ΔGRRGΔ, but no assembly or VLP budding for VP40E-ΔGEEGΔ, VP40E-ΔGMMGΔ, or VP40E-K274E/K275E. See also Figure S5 and Movie S1. *Scale bars = 500 nm.