July 19, 2004 | David F. Coppedge

You Have Motorized Sunscreens in Your Eyeballs

The pain of walking suddenly into a bright light sets up an amazing reaction, according to EurekAlert.  An alarm is sent to the fire station in the retinal cell.  There, protein firefighters hop onto a motorized shuttle on the molecular railway, and once firmly attached, are ferried swiftly to the scene of danger.  There, they shut off the energy flow which, if left untreated, could cause temporary blindness.  Here’s how the Johns Hopkins press release words it:

Building on their previous work showing that specific proteins in eye cells are redistributed in response to bright light, the Johns Hopkins team now reports how a key protein called arrestin is shuttled from a “holding area” where it binds and calms a light-detecting protein.  Writing in the July 7 issue of Neuron, the team says arrestin is moved around by a tiny molecular motor, called myosin, which travels along the “train tracks” of the cell’s internal skeleton.

This chemical reaction is separate from the muscular constriction of the iris that also automatically responds to the brightness of incoming light.

Wonder how many lucky accidents it took to put this system together.  Biology is beautiful when you take the Darwin dark glasses off.

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Categories: Amazing Facts, Human Body

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