The Other Protein Wisdom

August 19th, 2007 RWA Posted in News |

Not the excellent blog, but the exciting new announcement made by a team at the University of Oregon:

Scientists have determined for the first time the atomic structure of an ancient protein, revealing in unprecedented detail how genes evolved their functions.

“Never before have we seen so clearly, so far back in time,” said project leader Joe Thornton, an evolutionary biologist at the University of Oregon. “We were able to see the precise mechanisms by which evolution molded a tiny molecular machine at the atomic level, and to reconstruct the order of events by which history unfolded.”

…

The researchers focused on the glucocorticoid receptor (GR), a protein in humans and other vertebrates that allows cells to respond to the hormone cortisol, which regulates the body’s stress response. The scientists’ goal was to understand the process of evolution behind the GR’s ability to specifically interact with cortisol.

They used computational techniques and a large database of modern receptor sequences to determine the ancient GR’s gene sequence from a time just before and just after its specific relationship with cortisol evolved. The ancient genes — which existed more than 400 million years ago — were then synthesized, expressed, and their structures determined using X-ray crystallography, a state-of-the art technique that allows scientists to see the atomic architecture of a molecule. The project represents the first time the technique has been applied to an ancient protein.

The structures allowed the scientists to identify exactly how the new function evolved. They found that just seven historical mutations, when introduced into the ancestral receptor gene in the lab, recapitulated the evolution of GR’s present-day response to cortisol. They were even able to deduce the order in which these changes occurred, because some mutations caused the protein to lose its function entirely if other “permissive” changes, which otherwise had a negligible effect on the protein, were not in place first.

Ignoring the fact that x-ray crystallography is not exactly state-of-the-art (Max Von Laue won the Nobel Prize for its invention in 1914), the article does an excellent job of both explaining the work itself and its importance. Essentially, Thornton and Bridgham’s team has accomplished the biological equivalent of Wilson and Penzias’ discovery of the cosmic background radiation: they have traced the origins of life back to its original, elemental form, and “listened” to the protein “echo” to determine how successive changes arose. It’s another nail in the coffin of Irreducible Complexity, and another brick in the edifice of The Modern Synthesis of evolutionary and molecular biology.

In April 2006, a similar press release by Bridgham and Thornton’s team prompted a predictable tantrum from the Discovery Institute. We are still awaiting a similar outburst from them. In the meantime, smart people can discuss the actual science behind the news release in the Darwin Central forum.

UPDATE: Chris Street’s brand new blog offers a technical summary of the research, if you want to know the details.