Pitt Researchers Discover Protein Catenanes in virus of bacteria

Pittsburgh, September 26 -- University of Pittsburgh researchers today announced that they have discovered an entirely new type of catenane, rare molecular structures that link molecules in interlocking rings, in a virus that infects bacteria. Their findings, which could open the door to a new way of fighting harmful bacteria through "phage therapy," are detailed in a paper published in the September 22 edition of Science.

These catenanes are made of protein, and help create the protective outer shell of the bacterial viruses, called bacteriophages. Previously, catenanes had been observed only in DNA and small organic structures.

Bacteriophages, the most abundant form of life on earth, are microscopic creatures that vaguely resemble tadpoles, with a prominent head and tail, according to Roger W. Hendrix, a professor of biology and co-director of the Pittsburgh Bacteriophage Institute at the University of Pittsburgh. The proteins in their outer shell, called a capsid, are joined in an unusual ringed pattern similar to chain mail that provides the capsid with increased stability. Earlier experiments had strongly suggested the presence of such interlinked rings, but it was only with the new results that it has become possible to see the tiny structure directly, understand what makes it so strong, and determine how it gets assembled from its parts. The results reported today used the high-resolution technique known as x-ray crystallography.

"The protein links protect the virus the same way chain mail protected knights years ago," said Hendrix. "And, considering the severe environments in which phages are found, increased capsid stability may provide an evolutionary advantage to the phage."

The research, by Hendrix and fellow Pitt researcher Robert L. Duda, with colleagues from The Scripps Research Institute, the Stanford Synchrotron Radiation Laboratory, and the University of Uppsala, focused on a specific bacteriophage, HK97, but the findings are likely applicable to the entire class of tailed phages, called caudovirales.

"Phages are useful in a lot of different applications, from being 'guinea pigs' for basic biomedical research to practical applications in diagnostics and therapy. Every time we learn something fundamental about how they work, it helps us in all these areas," said Hendrix.

For more information on the Pittsburgh Bacteriophage Institute, access http://www.pitt.edu/~biohome/Dept/Frame/pbi.htm

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