Researchers find unusual protein in...( d protein databases where they observe...)

d protein databases, where they observed a DNA sequence encoding a previously unrecognized oxygen-binding protein in an anaerobic bacterium. This protein closely matched one that had previously been found only in a small group of marine organisms, including a species of worm (called "peanut worms") that live in the tidal flats of oceans. Until now, researchers had wondered why this protein was found only in this small group of marine organisms and not others.

The tidal flats where the worms live are a mostly anaerobic environment. However, unlike the anaerobic bacterium studied, the worms do not actively avoid oxygen and are not killed by it.

Researchers now believe that the protein has different functions in the two organisms, all related to their ability to detect oxygen. In the bacterium, the protein is for sensing and avoiding oxygen. In the worm, the protein appears to serve as an oxygen-storage reserve, providing oxygen whenever the worm needs it, says Kurtz.

This finding has evolutionary implications. "I'm suggesting that the bacteria developed the protein originally and that the worm sort of adapted it to do something different," says Kurtz.

The evolution of an oxygen-sensing protein was probably a matter of survival, he theorizes. Most scientists believe that the Earth's original atmosphere was devoid of oxygen and that, consequently, the first organisms to evolve were anaerobic. In this environment, the earliest bacteria probably did not need any structures to help them avoid oxygen because it was not a danger, the researcher says.

As the Earth evolved, plants emerged that steadily produced oxygen. The anaerobic bacteria had to either adapt or die in the new oxygen-rich atmosphere. That's when the bacteria began to evolve oxygen-sensing proteins, which were eventually incorporated by other organisms, Kurtz theorizes.

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Contact: Beverly Hassell
b_hassell@acs.org
202-872-4065
American Chemical Society
3-May-2000

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