Viruses Turnip yellow mosaic

Turnip yellow mosaic virus Turnip 13 + 5 Harris and Bindley (1961)... 

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) ... 

Virus coat proteins, capsids proteins with the largest known M, values (up to 40 x 10 ), lying on the exterior of the virus particle, enclosing the DNA or RNA. They comprise many, usually identical, subunits, called capsomeres (Af, 13,000-60,000). V.c.p. of tobacco mosaic virus consists of 2130 capsomers of M, 17,500. M, values of capsomeres from several strains of tobacco mosaic virus lie in the range 17,400-17,600 (157-158 amino acids) capsomeres of turnip yellow mosaic virus have M, 20,000 (188 amino acids). M, of bacteriophage capsids lie in the range M, 5,168 (49 amino acids) to M, 14,034 (131 amino acids). 

Column 3 RNA species. RNAs and pol mucleotides arranged alphabetically under each metal oxidation state and metal complex first by polyribonucleotide species, then by tRNA species in order of amino acid and then source organism, mixed (unfractionated) species listed after those identified by amino acid, and finally by RNA species other than tRNAs. Amino acids are abbreviated by the three letter nomenclature, Ala , Arg , etc. Met P and Met m .represent the translational initiator and the ordinary methionine spedes, respectively. TYMV=turnip yellow mosaic virus. TMV=tobacco mosaic virus. 

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].

On the other hand, Asselbergs et al. (1980) observed translational competition between globin mRNA, lens crystallin mRNAs, and turnip yellow mosaic virus RNA in the micrococcal nuclease-treated reticulocyte lysate, but not after microinjection into Xenopus oocytes (Asselbergs et al., 1979). The reason for this discrepancy is not clear, as Laskey et al. (1977) have shown that in oocytes, a component of the translation machinery, and not mRNA, limits the rate of protein synthesis. 

Turnip yellow mosaic virus (TYMV) amino acid sequences 13, 1 assembly 6, 3 nucleotide sequences 13, 2 translation 77, 3... 

The situation is more clear for the crystalline plant viruses some of which have been subjected to detailed comparative amino acid analysis and similar comparative nucleotide analysis (Knight, 150,151). All the plant viruses so far analyzed contain only one type of nucleic acid, i.e., RNA. The proportion varies from 6% for tobacco mosaic to 35% for turnip yellow mosaic virus. 

One distinguishes three classes of viruses (a) helical (rod-shaped) like TMV (Fig. 8.11), (b) spherical (of cubic symmetry) like turnip yellow mosaic virus (TYMV), Tipula iridescens virus (Fig. 8.12), and herpes virus and (c) complex symmetry like vaccinia or mumps virus and T-even phages (Fig. 8.13). 

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. 

Figure 2.9 Sedimentation coefficients of (left edge, top to bottom) 365 and 188 nm diameter polystyrene latex, turnip yellow mosaic virus, o -crystallin, y-globulin, serum albumin, and y-crystallin in solutions of 1.7 MDa hyaluronic acid, demonstrating that the ability of the polymer to retard sedimentation (as reflected in the concentration dependence of the normalized sedimentation coefficient s/sq) increases with increasing size of the sedimenting particle. Measurements are from Laurent and Pietruszkiewicz(4) and Laurent, et al. 5).

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