Figure 6

Model for STIV2 genome packaging. Schematic model for genome encapsidation of STIV2. The capsid of STIV2 is composed of A345, the major capsid protein (light blue hexagon). The host-attachment structures – the turrets – are composed of B631 (dark blue triangles) and the membrane protein A55 (black spheres), as described for STIV [81]. The capsid encloses the viral lipid membrane (yellow), with several predicted membrane proteins (orange spheres) attached to it. The membrane proteins E51 and E76b are proposed to form a pore in the membrane for STIV2 genome translocation at the packaging vertex [7]. STIV2 assembly initiates by the formation of the procapsid. We have proposed that the postulated STIV2 genome recognition protein B72 (green sphere) would simultaneously recognize and bind to the STIV2 genome, forming the initiation complex thus recruiting the viral genome for packaging [7]. According to our hypothesis, the initiation complex is recognised by the genome packaging ATPase B204 that has assembled as a hexamer (red) at the packaging vertex. The STIV2 genome is translocated into the procapsid via ATP powered hydrolysis. The figure is redrawn from [7].