Researchers at Genentech Inc. and Harvard Medical School havedetermined the structure of a potent clot-dissolving protein in thevenom of pit vipers.

Kistrin is a sugar-protein that blocks the adhesion of platelet cellsto fibrinogen in the bloodstream, thereby preventing platelet-richclots from forming.

The researchers, reporting today in Science, used nuclear magneticresonance spectroscopy to show that kistrin has a recognitionsequence of amino acids that are important for binding to thesurface integrin receptor of platelets. The recognition sequence isat the apex of a long strand that loops across kistrin's surface.

Kistrin shows promise as a booster for the clot-dissolving abilitiesof tissue plasminogen activator in dogs, the scientists wrote.Knowledge of its structure may aid design of new antagonists ofplatelet adhesion. -- Roberta Friedman, Ph.D.

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