Comparative studies of T = 3 and T = 4 icosahedral RNA insect viruses.
Crystallographic and molecular biological studies of T = 3 nodaviruses (180 identical subunits in the particle) and T = 4 tetraviruses (240 identical subunits in the particle) have revealed similarity in both the architecture of the particles and the strategy for maturation. The comparative studies provide a novel opportunity to examine an apparent evolution of particle size, from smaller (T = 3) to larger (T = 4), with both particles based on similar subunits. The BBV and FHV nodavirus structures are refined at 2.8 A and 3 A respectively, while the N omega V structure is at 6 A resolution. Nevertheless, the detailed comparisons of the noda and tetravirus X-ray electron density maps show that the same type of switching in subunit twofold contacts is used in the T = 3 and T = 4 capsids, although differences must exist between quasi and icosahedral threefold contacts in the T = 4 particle that have not yet been detected. The analyses of primary and tertiary structures of noda and tetraviruses show that N omega V subunits undergo a post assembly cleavage like that observed in nodaviruses and that the cleaved 76 C-terminal residues remain associated with the particle.
Department of Biological Sciences, Purdue University, West Lafayette, Indiana.
J E
JE
Johnson
S
S
Munshi
L
L
Liljas
D
D
Agrawal
N H
NH
Olson
V
V
Reddy
A
A
Fisher
B
B
McKinney
T
T
Schmidt
T S
TS
Baker
D018360:Crystallography, X-Ray; D007304:Insect Viruses / Q000145:classification / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008958:Models, Molecular; D008961:Models, Structural; D008968:Molecular Conformation; D012328:RNA Viruses / Q000145:classification / Q000648:ultrastructure*