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12. Structures of Viruses

Viruses consist mainly of protein and nucleic acid and their organization is of particular interest because they represent a form of life and because they may be crystallized. Two examples, a rod-like virus and a spherical virus, are described here.

Tobacco mosaic virus (TMV) is a rod-like virus 3000 Å long and 90 Å radius with a central hole of radius 20 Å. Identical protein subunits (MW 17,500) form 49 subunits in 3 turns protecting the RNA. Isomorphous replacement was applied to the fibre diagram of TMV. The general conformation could be deduced.

Tobacco bushy stunt virus (TBSV) is a spherical virus that crystallizes in a cubic cell a = 383 Å, space group I23. The virus coat is built from protein subunits having rigid domains connected by a flexible hinger. Each subunit has a binding site for RNA on its inner surface.

Neutron scattering of virus solution is used to obtain low resolution information on viral nucleic acid since H₂O-D₂O mixtures can be made with scattering powers that match either RNA or protein.

References

1. Virus architecture. Caspar, D. L. D. and Klug, A., Cold Spring Harb. Symp. Quant. Biol . 27 (1962) 1.

2. The assembly of a virus. Butler, P. J. G. and Klug, A., Scientific American 239 (1978) 62.

3. Tobacco mosaic virus. Protein disk. Champness, J. N., Bloomer, A. C., Bricogne, G., Butler, P. J. G. and Klug, A., Nature 259 (1976) 20; Bloomer, A. C., Champness, J. N., Bricogne, G., Staden, R. and Klug, A., Nature 276 (1978) 362.

4. Tobacco bushy stunt virus. 5.5 Å resolution. Winkler, F. K., Schutt, C. E., Harrison, S. C. and Bricogne, G., Nature 265 (1977) 509; Harrison, S. C., Olson, A. J., Schutt, C. E., Winkler, F. K. and Bricogne, G., Nature 276 (1978) 368: Robinson, I. K. and Harrison, S. C., Nature 297 (1982) 563.

5. Neutron small angle scattering. Jacrot, B., Chauvin, C. and Witz, J., Nature 266 (1977) 417.

Next: Acknowledgement Up: Elementary X-Ray Diffraction for Biologists Previous: Transfer RNA

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