A protein is like a tiny machine that switches on and off on command. The command arrives when another molecule sticks to it, like a key in a lock. The protein then changes shape and passes the signal along. But exactly how the signal travels inside the protein has long been a mystery.
Now scientists have combined two methods: ultrafast laser imaging and computer simulation. The laser flash heats the protein, making it move, while the computer replicates those motions on screen. By comparing the images, researchers identified which parts of the protein move first and which move later. It turns out the signal travels along a chain of several amino acids, like a relay race where the baton is passed from one runner to the next.
This method works for different proteins. For example, the scientists tested it on the PDZ3 protein, which transmits signals in cells, and on PDZ2, which releases a captured molecule when exposed to light. In both cases, they were able to see the signal race through the protein in billionths of a second. Such knowledge could help design drugs that hit their targets precisely and understand why proteins sometimes malfunction and cause disease.
A protein can pass a signal in one billionth of a second — faster than a light bulb blinks.