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Capsid of bacteriophage T4 virus
This figure shows the capsid, or outer shell, of a virus called bacteriophage T4. Proteins called gp23 are represented in blue and gp24 are represented in magenta. Both of these proteins are critical for the assembly of the T4 capsid.
More about this Image
Researchers have found the T4 virus and another virus called HK97 both have similar protein folds in their outer shells. These findings are providing further evidence that the protein envelope protecting DNA in viruses evolved billions of years ago from a common ancestor and uses the same basic protein fold to construct the outer shell. Researchers used X-ray crystallography to view the gp24 protein at a resolution of 2.9 angstroms and electron microscopy to view the virus capsid at 22-angstrom resolution. An angstrom is one ten-billionth of a meter, or roughly 1 millionth as wide as a human hair.
This National Science Foundation-funded research is aimed at understanding the structures of viruses. (Date of Image: May 18, 2005)
Credit: Image courtesy Purdue University Department of Biological Sciences
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