Satellite tobacco necrosis virus, STNV

Satellite viruses are those that are dependent for their own replication on some (catalytic) activity encoded in another helper virus that coinfects the host cell. The structures of three plant ssRNA satellite viruses represent some of the highest resolutions known and have been comparatively reviewed (Ban et al., 1995). The structures of satellite tobacco mosaic virus (STMV) (Larson et al., 1993a,b), satellite tobacco necrosis virus (STNV) (Jones and LUjas, 1984 Liljas et al., 1982), and satellite panicum mosaic virus (SPMV) (Ban and McPherson, 1995) have T=1 capsids composed of 60 identical copies of unembellished jelly-roll j3 barrels constructed of only 155 to 195 amino acids (Fig. la see Color Insert). What is remarkable is how little the assembly context of these domains is conserved. The same end always points toward the 5-fold axis, but the domains are rotated to different extents around the 5-fold axis. Furthermore, between STNV and the others, there is a 70° rotation of the barrel about its long axis. Contacts across the dimer interface are... 

The satellite ssRNA viruses are a group of ssRNA icosahedral viruses, which are the satellites to certain plant viruses (Pritsch and Mayo, 1989). Satellite tobacco necrosis virus (STNV), a satellite virus to tobacco necrosis virus, was in fact one of the first icosahedral virus structures to be determined by X-ray crystallography (Liljas et al, 1982). In more recent years, two other satellite plant viruses, satellite tobacco mosaic virus (STMV) (Larson et al, 1993, 1998) and satellite panicum mosaic virus (SPMV) (Ban and McPherson, 1995), have been determined. These are perhaps the simplest and smallest icosahedral viruses whose structures have been determined by X-ray crystallography. Of relevance to our discussion is the structure of STMV determined to 1.8-A resolution, which shows extraordinary details about genome organization (Larson et al, 1998 Larson and McPherson, 2001). 

RNA structure and, 49-50 satellite tobacco necrosis virus (STNV) and, 49-50... 

Fig. 14.16. Nanoscaled systems of the biosphere and of chemistry show the same topology schematic representation of the icosahedron spanned by the 12 centres of the (Mo)IVIo5 units of the M0132 type cluster (a) and of the satellite tobacco necrosis virus (STNV) with the triangulation number F = 1...

This molecular system with its 60 MoOe subunits, corresponding to the 12 related (Mo)Mo5 pentagons, represents a topological model for spherical viruses, e.g., the most simple satellite tobacco necrosis virus (STNV) with... 

Satellite tobacco mosaic vims (STMV), 153, 222-225 encapsidated genome of, 223 Satellite tobacco necrosis vims (STNV), neutron scattering and, 49-50, 222 Satellite viruses, viral stmcture taxonomy and, 139-141, 139... 

These experiments have been dissapointing in the sense that the only features which seem to be universal are the AUG initiation codon and the 5 cap structure (7I, 72), and even the latter is missing from some viral RNAs, notably picornavirus RNAs (both the virion RNA (75) and. the viral mRNA (74)), Cowpea Mosaic Virus (CPMV) RNA (75)f and Satellite Tobacco Necrosis (STNV) RNA (76). The role of the cap has been studied by examining the properties of mRNA... 

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