"We have genes in our body coding for proteins, but proteins get modified in lots of different ways, one of which is by addition of sugars that stick out on the cell surface and change the way the protein interacts with the environment," Amacher said. "One of the big mysteries is how the pattern of sugar modification changes during development, or in cancer cells versus non-cancer cells, for example. The exciting work Carolyn is now doing is finding ways that we can actually see the sugar labels on proteins."
Scientists have known for more than a century how to attach fluorescent dyes to proteins, and have used the technique to study protein trafficking in cell culture and even in whole organisms, though often at the expense of killing the cells or organism. Bertozzi has focused on making it just as easy to study the sugars on cells, in part to investigate their role in such diseases as tuberculosis and influenza. In the latter, the flu virus enters cells by way of hemagglutinin, a sugar-protein complex on the viral surface that attaches to sugars on the surface of host cells. But sugars clearly have roles in cell-to-cell communication that have yet to be discovered.
One technique Bertozzi has developed is to feed cells an artificial sugar that looks so much like the real thing that cells are tricked into incorporating the sugar into their carbohydrate chains. Once the sugar becomes part of the forest of carbohydrates adorning a living cell, she then uses a non-toxic chemical reaction to attach small organic labels to it. Simple, highly selective and non-toxic chemical reactions like this have come to be called click chemistry.
In their work on zebrafish, Baskin, Bertozzi and their colleagues soaked zebrafish embryos in the artificial sugar N-azidoacetylgalactosamine, whic
|Contact: Robert Sanders|
University of California - Berkeley