Tobacco mosaic virus: application of the method of isomorphous replacement to the determination of the helical parameters and radial density distribution

Franklin, Rosalind; Holmes, Kenneth C.

doi:10.1107/s0365110x58000529

Cited by 138 publications

(30 citation statements)

References 9 publications

(14 reference statements)

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“…The positions of the remaining equatorial peaks in Fig. 1 A are consistent (26) with continuous diffraction from a filament approximating a solid cylinder of diameter 55 Å. They might also be explained by arrays of regularly-spaced fibrils of any structure, but this explanation is inconsistent with the complete absence of low-angle diffraction from some fibers.…”

Section: Resultsmentioning

confidence: 54%

Natural and synthetic prion structure from X-ray fiber diffraction

Wille

Bian

McDonald

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

199

226

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A conformational isoform of the mammalian prion protein (PrP Sc ) is the sole component of the infectious pathogen that causes the prion diseases. We have obtained X-ray fiber diffraction patterns from infectious prions that show cross-␤ diffraction: meridional intensity at 4.8 Å resolution, indicating the presence of ␤ strands running approximately at right angles to the filament axis and characteristic of amyloid structure. Some of the patterns also indicated the presence of a repeating unit along the fiber axis, corresponding to four ␤-strands. We found that recombinant (rec) PrP amyloid differs substantially from highly infectious brainderived prions, both in structure as demonstrated by the diffraction data, and in heterogeneity as shown by electron microscopy. In addition to the strong 4.8 Å meridional reflection, the recPrP amyloid diffraction is characterized by strong equatorial intensity at approximately 10.5 Å, absent from brain-derived prions, and indicating the presence of stacked ␤-sheets. Synthetic prions recovered from transgenic mice inoculated with recPrP amyloid displayed structural characteristics and homogeneity similar to those of naturally occurring prions. The relationship between the structural differences and prion infectivity is uncertain, but might be explained by any of several hypotheses: only a minority of recPrP amyloid possesses a replication-competent conformation, the majority of recPrP amyloid has to undergo a conformational maturation to acquire replication competency, or inhibitory forms of recPrP amyloid interfere with replication during the initial transmission.amyloid ͉ protein ͉ neurodegeneration ͉ PrP ͉ ␤-helix

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Section: Resultsmentioning

confidence: 54%

Natural and synthetic prion structure from X-ray fiber diffraction

Wille

Bian

McDonald

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

199

226

View full text Add to dashboard Cite

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“…3. This is a reasonable value when compared with that estimated on the basis of the radial electron density distribution for tobacco mosaic virus (Franklin & Holmes, 1958). It can be seen from that the effect of the hole is to displace the first zero position of the transform and this accounts for the observed (1,0) reflection.…”

Section: X-ray Diffractionsupporting

confidence: 52%

Diffraction Studies of Tulip Virus X Particles

Radwan

Wilson

Duncan³

1981

Journal of General Virology

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SUMMARYX-ray diffraction from oriented tulip virus X (TVX) particles and optical diffraction from electron micrographs show that the virus particles have a helical structure with a pitch of about 3.25 nm and a true repeat in five turns of the helix. Both X-ray and optical diffraction indicate that the number of subunits in the repeat period is 5q + 4, where q is an integer. The X-ray diffraction patterns suggest that 9 /> q/> 6, and the optical diffraction patterns suggest that q is probably 7 or 8. The X-ray diffraction patterns indicate that there is a marked feature in the virus particle at a radial position of about 3.3 nm, which is probably the RNA. The equatorial diffraction further suggests that the virus has an axial hole of about 1.5 nm radius.

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“…2A) at resolutions between 65 Å and 22 Å. The origin peak (data inside the equatorial node at 110 Å) was calculated from a solid cylinder, scaled in amplitude to the low-angle amplitudes and radially to the first node position (26,34). The positions of the peaks in the distribution are probably influenced by series termination error; they remain even when very large temperature factors are imposed upon the equatorial amplitudes, but their positions depend on the resolution of the input data.…”

Section: Resultsmentioning

confidence: 99%

“…In consequence, diffracted amplitude maxima that are sufficiently close together must have alternating signs. The minimum-wavelength principle was used by Caspar (13) in TMV studies, and the signs determined for TMV were subsequently shown by isomorphous replacement to be correct (26,48).…”

Section: Methodsmentioning

confidence: 99%

Structure of Flexible Filamentous Plant Viruses

Kendall

McDonald

Bian

et al. 2008

J Virol

100

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Flexible filamentous viruses make up a large fraction of the known plant viruses, but in comparison with those of other viruses, very little is known about their structures. We have used fiber diffraction, cryo-electron microscopy, and scanning transmission electron microscopy to determine the symmetry of a potyvirus, soybean mosaic virus; to confirm the symmetry of a potexvirus, potato virus X; and to determine the low-resolution structures of both viruses. We conclude that these viruses and, by implication, most or all flexible filamentous plant viruses share a common coat protein fold and helical symmetry, with slightly less than 9 subunits per helical turn.Flexible filamentous plant viruses include at least 19 recognized genera (22), almost all in three families of singlestranded, positive-sense RNA viruses, the Potyviridae, the Flexiviridae, and the Closteroviridae. Members of the family Potyviridae account for almost a third of the total known plant virus species (22) and are responsible for more than half the viral crop damage in the world (37), infecting most economically important crops (32). Members of the family Flexiviridae (2), and particularly of the large genus Potexvirus, are also of considerable significance to agriculture (42). Both families show great potential for biotechnological applications, including protein expression and vaccine production (12, 54). Despite their importance, however, little is known about the structures of any of the flexible filamentous plant viruses, in sharp contrast to the amount of data on the rigid tobamoviruses (48,63) or the icosahedral plant viruses (15); flexibility, instability, and in many cases low levels of expression have made these viruses particularly intractable to structural studies. Structural and evolutionary relationships among the flexible filamentous plant viruses have been suggested (18,47,56,60), but there is very little sequence homology between the coat proteins of viruses in the different families, and there has hitherto been no structural support for such relationships at the level of either viral symmetry or coat protein folding. Indeed, reports of viral symmetry until now appeared to contradict hypotheses of evolutionary relationships.Soybean mosaic virus (SMV) is a potyvirus, that is, a member of the genus Potyvirus, the largest genus in the family Potyviridae (3). SMV is a major pathogen of soybeans, transmitted efficiently through seed and by aphids in a nonpersistent manner; yield losses as high as 35% have been reported (30). Despite dramatic morphological differences, members of the family resemble the icosahedral plant comoviruses and animal picornaviruses in genomic organization and replication strategy (32). Early electron microscopic observations found the potyviruses to be about 7,500 Å long and 120 Å in diameter, with helical pitches of about 34 Å (44, 60). A fiber diffraction study (51) of the tritimovirus wheat streak mosaic virus (WSMV) suggested that WSMV has 6.9 subunits per turn of the viral helix, but there was consider...

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Tobacco mosaic virus: application of the method of isomorphous replacement to the determination of the helical parameters and radial density distribution

Cited by 138 publications

References 9 publications

Natural and synthetic prion structure from X-ray fiber diffraction

Natural and synthetic prion structure from X-ray fiber diffraction

Diffraction Studies of Tulip Virus X Particles

Structure of Flexible Filamentous Plant Viruses

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