Chemists: Proteins may guide evolution

“What we have found is that certain kinds of biological structures exist that are able to steer the process of evolution toward improved fitness,” chemistry professor Herschel Rabitz said in a University statement. “The data just jumps off the page and implies we all have this wonderful piece of machinery inside that’s responding optimally to evolutionary pressure.”

Rabitz and University researchers Raj Chakrabarti, Stacey Springs and George McLendon focused their efforts on ETC proteins, which are responsible for producing adenosine triphosphate (ATP), the energy currency used by cells.

The ETC uses electrons to alter the concentrations of ions on either side of the mitochondrial membranes, and the resulting potential-energy gradient is used to produce ATP. What is remarkable is that the strength of the gradient has a direct relationship to an organism’s fitness, and a stronger gradient allows more ATP to be produced, according to the study.

The ETC’s ability to take electrons — its redox potential — has no direct relationship to fitness, but it exhibited evolutionary trends as if it did. The researchers studied this effect by inducing mutations in the ETC proteins that altered their redox potential, and they found that, over time, proteins were able to correct these mutations such that they were operating functionally again.

The researchers mathematically analyzed the behavior of proteins in which mutations had been induced and found trends that indicated that proteins could control their own evolution by preventing errors from accumulating and becoming lethal.

This observation has implications for the entire field of evolutionary biology, Chakrabarti explained in a University statement.

“The discovery answers an age-old question that has puzzled biologists since the time of Darwin,” Chakrabarti said. “How can organisms be so exquisitely complex, if evolution is completely random, operating like a ‘blind watchmaker’?”

Darwin, who published “On the Origin of Species by Means of Natural Selection” in 1859, hypothesized that species evolve as a result of external pressures through natural selection. He posits that organisms with more advantageous traits are more likely to survive and contribute their genes to subsequent generations.

One of the major criticisms of evolutionary theory, however, is that the development of intricate structures, such as eyes, cannot be the result of a gradual accumulation of random mutations.

The group’s research suggests that even at the protein level, intrinsic characteristics can help steer the evolution of an organism, “creat[ing] order out of randomness,” Chakrabarti said.

Though Darwin’s theory of evolution did not predict this internal monitoring ability, a related theory, proposed by fellow British biolgoist Alfred Wallace, did.

Wallace, a contemporary of Darwin, independently reached similar conclusions about evolution, but Darwin ultimately is better remembered throughout history because, following collaboration between the two men, it was the work of Darwin that was published.

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Wallace proposed the possibility that systems within organisms had developed the ability to monitor themselves and keep their development in check, drawing comparisons to the centrifugal governor that keeps steam engines functioning properly through what is now known as feedback control.

What remains for future research to determine is the actual mechanism by which the proteins are able to counter mutations to their structure, according to the study. Nevertheless, a significant discovery has already been made. While natural selection acts from the outside and guides the evolution of species, internal factors may play an equally important role.

Proteins, it turns out, can steer their own evolution.