Tobacco mosaic virus structure studies

Recent Studies on the Structure of Tobacco Mosaic Virus F. Alfred Anderer... 

II A radically different type of nucleoprotein is that provided by the smaller RNA viruses of the elongated spiral type like tobacco mosaic, or of the polyhedral type such as tomato bushy stunt, tipula virus or poliomyelitis virus. The only one of these adequately studied has been tobacco mosaic virus, Franklin [19, 20], and here it appears that the protein and not the nucleic acid determines the structure. There is only one RNA chain and this is wound helically so that one protein is in contact with three successive nucleotides. 

Both X-ray and neutron fiber diffraction (as well as electron microscopy) techniques have been applied to filamentous viruses, for which the prospect of three-dimensional crystals is poor. By combining neutron and X-ray fiber diffraction, NMR, circular dichroism, and Raman and infrared spectroscopies, an atomic model for the filamentous bacteriophage Pfl has been derived (Liu and Day, 1994). Other studies concerning Pfl have relied on purely X-ray fiber diffraction data, together with molecular modeling, to provide detailed filament structures (Pederson et at, 2001 Welsh et at, 1998a,b, 2000). Eiber diffraction was also used to solve the structure of the rodlike helical tobacco mosaic virus (TMV), where all of the coat protein and three genomic nucleotides... 

The tobacco mosaic virus was selected as model for complex assemblies involving biopolymers. AFM in selected media helps to clarify the structure of such assemblies under different conditions and eventually may allow one to study details of the biological function in situ. 

As early as 1938, Langmuir observed the phase separation of clay suspensions into an isotropic phase and a birefringent gel at the macroscopic level in test-tubes [9]. However, in the same report, he noted that this property of phase separation was gradually lost with time, which he tentatively explained by the incorporation of impurities diffusing from the glass tubes. He also compared this system to normal liquid crystals. Later, in 1956, Emerson observed a banded texture similar to that displayed by the Tobacco Mosaic Virus [48]. The investigation of clay suspensions from the structural point of view has been recently resumed. However, the study of the nematic order of suspensions of montmorillonite clays is in fact complicated by their gel properties. In spite of sustained efforts to understand its nature, the gelation mechanism has not yet been fully elucidated [49]. 

Filamentous viruses, which are high-aspect ratio agents that proliferate in the presence of host cells, have regular self-assembled structures, and the viral coat proteins on their surface can be genetically or chemically modified to functionalise the nanovector. The tobacco mosaic virus is one of the most extensively studied ID structure for nanoscale applications, and their properties, functionalisation, and assembly into nanodevices are highlighted in the recent review by Ghodssi and co-workers. Mao and co-workers have recently demonstrated that filamentous bacteriophage can be converted into novel photo-responsive nanowires... 

Tubules with hollow cavities through self-assembly of small molecules are a major structural feature of biological systems, as exemplified by tobacco mosaic virus and cytoplasmic micrombules [15,16]. Many studies have focused on the nanostructures through self-assembly of lipid molecules [17], aromatic amphiphiles [18-22] and oligopeptides [23,24] using various non-covalent interactions [25]. Also, the... 

In 1936 Mirsky and Pauling recognized the role of hydrogen bonds as important determinants of the secondary and tertiary structure of the proteins, in addition to intra-and interchain S—S linkages and ionic forces. More than a decade later hydrophobic interactions between certain amino acids were added as important conformational factors. That non-covalent linkages between proteins and non-protein compounds can determine the quaternary structure of a protein was shown in 1957 by the reconstitution of the tobacco mosaic virus from its isolated RNA and protein parts by Fraenkel-Conrat. On the other hand, Anfinsen< > could show that when the tertiary structure and activity of the bovine pancreas RNase are destroyed by reduction of its S—S linkages, re-oxidation of the SH groups finally leads to complete restitution of the enzymatic activity. Further structural studies of the reconstituted active enzyme support the assumption that in this case initial tertiary structure of the protein was restored. This supports the assumption that the tertiary structure of a protein is defined by its amino acid sequence. 

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