Anyone suffering from a cold knows how tough and persistent viruses can be.

Now scientists have discovered that one type of virus actually comes equipped with an armored coat made of interlocking rings of protein.

The structure of this virus - remarkably similar to chain mail suits worn by medieval knights - had been predicted but never directly observed in a protein until now. Researchers say the discovery could have applications for the booming field of nanotechnology.

The armored virus was detected by an international team of scientists from Stanford, the Scripps Research Institute, the University of Pittsburgh and the University of Uppsala in Sweden. Their findings are published in the Sept. 22 issue of the journal Science.

A typical virus consists of little more than a chromosome of DNA or RNA wrapped in a protein coat.

Although viruses are among the simplest microbes, determining their molecular structure requires very sophisticated instrumentation.

The authors of the Science study used special micro-imaging techniques to analyze the outer coating of a virus called bacteriophage HK97.

Bacteriophages are viruses that only infect bacteria. They come in very bizarre shapes, some of which resemble NASA-designed satellites or Martian landers.

HK97 is no exception. It has an odd, balloon-shaped head attached to a short tail.

Analyzing this strange protein exterior required both electron microscopy and X-ray crystallography, says Hiro Tsuruta, a senior research associate with the Stanford Synchrotron Radiation Laboratory (SSRL) and the Department of Chemistry.

"The head of the virus is thousands of times narrower than a human hair," adds Tsuruta, a co-author of the Science study.

With the help of a small angle X-ray diffraction instrument at SSRL, Tsuruta and his colleagues were able to determine that HK97's head is made of 72 protein rings - 12 pentagons and 60 hexagons
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
21-Sep-2000