

Scientists have assembled the highest-resolution image yet of the protein sheath that surrounds viral DNA, accurate right down to the last of its five million atoms.

Called a capsid, the sheath protects viral DNA from cellular defense mechanisms. If scientists can crack it, they might have a clear shot at the virus — and now they know what it looks like.

The image, published Monday in the Proceedings of the National Academy of Sciences, was made from hundreds of crystallographic x-rays, each providing a multi-layered picture of the capsid's structure. Combined, they formed a fully three-dimensional image.

With it, researchers were able to show the capsid's composition from repeating copies of a single four-protein block. Earlier studies had identified the protein, but not its precise arrangement.

The researchers used a capsid belonging to Penicillium stoloniferum, a virus that infects the fungus that makes penicillin, but the findings may be applicable to the several hundred viruses that share its spherical capsid shape. Other viruses have helical capsids; images still need to be assembled for them, but the same imaging techniques may be applied.

Image: J. Pan & Y.J. Tao / Rice University

Citation: "Atomic structure reveals the unique capsid organization of a dsRNA virus." By Junhua Pan, Liping Dong, Li Lin, Wendy F. Ochoa, Robert S. Sinkovits, Wendy M. Havens, Max L. Nibert, Timothy S. Baker, Said A. Ghabrial, and Yizhi Jane Tao. Proceedings of the National Academy of Sciences, Vol. 106 No. 7, Feb. 16, 2009.

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