The filamentous plant viruses of the family Potyviridae include almost a quarter of the known plant viruses. The family includes the genera Potyvirus, Rymovirus, Tritimovirus, Bymovirus, Maclurovirus, Ipomovirus and Brambyvirus. Potyvirid particles are approximately 7500 Å long and 120 Å in diameter and have helical pitches of about 33 Å. Circular dichroism measurements and secondary structure predictions suggest that the coat proteins are about 50% α-helical, similar to the potexviruses, and that the N- and C-termini of the coat proteins are located near the surface of the virions. Little other structural information was available for members of this family until recently. This paper shows that the potyvirids exhibit significant variation in helical symmetry, like the potexviruses and unlike the tobamoviruses.
Architecture of the potyviruses. Virology. Jul 1 2010 doi: 10.1016/j.virol.2010.06.013
X-ray fiber diffraction data were obtained and helical pitch and symmetry were determined for seven members of the family Potyviridae, including representatives from the genera Potyvirus, Rymovirus, and Tritimovirus. The diffraction patterns are similar, as expected. There are, however, significant variations in the symmetries, as previously found among the flexible potexviruses, but not among the rigid tobamoviruses. Wheat streak mosaic virus, the only member of the genus Tritimovirus examined, displayed the largest deviations in diffraction data and helical parameters from the other viruses in the group.