Architecture of SGIV outer coat. The components include the pentamer at the 5-fold vertex, hexameric trimers making up pentasymmetrons (purple) and trisymmetrons (blue and cyan), anchor proteins (orange), and zip proteins (red and orange). The zip proteins are made up of a ‘level’ component which is level to the inner surface, and an arch component which curves inwards towards (but not touching) the lipid membrane. The arch component is found between trimers in adjacent trisymmetrons, but not between trimers in adjacent penta and tri-symmetrons.