Turnip yellow mosaic virus, structure

Cosslett, V. E., u. R. Markham Structure of turnip yellow mosaic virus... 

These conclusions were placed in some doubt when it was subsequently shown that (a) turnip yellow mosaic virus, which produced an X-ray diffraction pattern virtually identical to that of poliovirus, had a capsid composed of 180 identical structural polypeptides arranged in quasiequivalent hexamer-pentamer clusters to give 52 morphological units or capsomeres (29) (b) the poliovirus capsid was composed of not one but several non-identical polypeptide species (15)> and (c) the assumed particle weight and t the RUA molecular weight for poliovirus were not correct (2, 3> 4) ... 

Table 19.2a Variation of aminoacyl-tRNA using T. thermophilus EF-Tu GTP. Asp-tRNA originates from yeast and is fully modified. A minihelix consists of two RNA oligonucleotides derived from aminoacyl arm of tRNA. The number of base pair counted from aminoacyl end is indicated in parentheses. His-TYMV RNA is an aminoacylated tRNA-like structure originating from turnip yellow mosaic virus. AEDANS indicates that the fluorescence reporter group was used as an indicator for the measurements of the interaction with EF-Tu GTP whereas 2 or 3 dA, 3 NH, and oxi/red denote different non-isomerisable aminoacyl-tRNAs [28].

Althou the RNA molecule of most plant viruses contains no fewer than two or three structural cistrons, on entering the cell it becomes the template for synthesis of two or three virus-specific proteins (just as in the case of messenger RNA) without fragmentation into mono cistronic segments In this case, one template links itself to the ribosomes and carries out the synthesis of several proteins simultaneously. Indirect evidence obtained during the study of polysomes formed by RNA or turnip yellow mosaic virus (mol. wt. of RNA 2.3 x 10 ) show that each cistron of the template can work as an independent template, rather than in turn after its neighbor (Voorma, Gout, et al., 1964). This type of operation of the template is necessary because different proteins from different parts of the template are synthesized in different quantities. 

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