Protein Matchmaking & Salt Bridges
A Water-Repellent Zipper
Steven McKnight and his colleagues, then at the Carnegie Institution of Washington, first postulated that the leucine zipper existed in 1987. Subsequent research confirmed it and showed that this structural motif is a pair of protein coils wrapped around each other, similar to the twin strands of the DNA double-helix. At the innermost overlapping point of the coils, occurring every seventh position in a regular pattern, is leucine. Leucines are hydrophobic -- literally "water fearing" -- and they attract each other, so that by coming together at the coil interface, they shelter themselves from the surrounding water.
A critical function of leucine-zipper proteins is to bring together the right protein coils so the dimer can properly carry out its biological task, whether activating a gene or some other function. "By matching the right proteins at the right time," says Tidor, "the leucine zipper choreographs key cellular events, and an important question is what interactions control which coils associate."
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