A KNOT has been found in a protein made by a primitive bug called Methanobacterium thermoautotrophicum. While knots in proteins aren鈥檛 unheard of, they are still rare. And no one knows how they form or how they affect protein behaviour.
Finding a knot in such an ancient bacterium indicates that they must have some use, says co-author Andrzej Joachimiak from the Argonne National Laboratory in Chicago. 鈥淓volution doesn鈥檛 hold on to things it doesn鈥檛 need,鈥� he says. Perhaps the knot might help the protein hold together at high temperatures, he suggests (Proteins, vol 50, p 177).