Knotty problem puzzles protein researchers by Anne Trafton:
Knots are rare in proteins–less than 1 percent of all proteins have any knots, and most are fairly simple. The researchers analyzed 32,853 proteins, using a computational technique never before applied to proteins at this scale.
Of those that had knots, all were enzymes. Most had a simple three-crossing, or trefoil knot, a few had four crossings, and the most complicated, a five-crossing knot, was initially found in only one protein–ubiquitin hydrolase.
That complex knot may hold some protective value for ubiquitin hydrolase, whose function is to rescue other proteins from being destroyed–a dangerous job.
Photo: MIT researchers recently found that human ubiquitin hydrolase, shown here, has the most complicated knot ever observed in a protein. The simplified diagram, inset, shows the knot in the protein, which crosses itself five times. Larger image.
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