The rule of biochemically simple biochemistry drives the evolution of useless complexity

New research shows that proteins become biochemically dependent on complex interactions without adapting.

New study University of Chicago has shown that complex protein structures accumulate over a long period of time, even when they do not serve any purpose, as the universal biochemical property և genetic code forces their natural preservation. The work was published in 2020. On December 9, c Nature:,

Most of the proteins in our cells make up specific proteins in combination with other proteins, a process called multiplication. Like other types of biological complications, it is commonly believed that multimers continue to evolve over time, as they provide some functional benefit that prefers natural selection.

“How complexity develops is one of the most important questions in evolutionary biology,” said Joseph Ozef Thornton, PhD, Senior Author, PhD in Human Genetics and Ecology at the University of Chicago. “The classic explanation is that complex structures must exist, as they provide some functional benefit to the body, so natural selection leads to ever-increasing complexities. It is obvious that in some cases the complication adapts to the evolution of the eye. Complicated eyes see better than ordinary eyes. But at the molecular level, we found that there are other simple mechanisms that drive complexity. ”

The research team led by Thornton համալս PhD, University of Chicago, Ph.D. Georg Hochberg set out to study the evolution of multimerization in a family of proteins called steroid receptors, which come together in pairs (called dimers).

They used a method called ancestral protein recovery, a kind of molecular “time travel,” says Thornton, which allows them to recreate old proteins in the laboratory and experimentally study how they were affected by mutations that occurred. hundreds of millions of years ago.

To their surprise, they found that the ancient proteins worked lower than if they had never been developed to darken at all. There was nothing useful in the construction of the complex.

The explanation for why the receptor dimer is stored for 450 million years is clear. “These proteins have become increasingly dependent on their interaction, although there is nothing useful about it,” said Hochberg, who now heads the group at the Max Planck Institute in Marburg, Germany. “The parts of the protein that make up the interface, when the partners bind the accumulated mutations, which allowed after the development of the did, but would be harmful in a solo state. This protein was completely dependent on the dimeric egg, it could not go back. The useless complication took root, essentially forever. ”

Researchers have shown that simple biochemical, genetic, evolutionary principles make molecular complexity inevitable. The genes encoding each protein are constantly mutated during generations of hail, many of which impair the ability of the protein to fold and function properly. The natural selection egg, called the cleansing choice, removes these harmful mutations from the population.

As the protein undergoes multiplication, the components of the interface can accumulate mutations that would be harmful if the protein were solo for as long as they could be tolerated in a multimeter. The cleansing choice then infects the complex egg, preventing it from returning solo.

Researchers have shown that the simple universal rule of biochemistry is based on rooting. Proteins are made up amino acids, which can be dissolved in water or hydrophobic, ie they are easily soluble in oil but not in water. Proteins are usually folded so that the water-soluble amino acids are on the outside and the hydrophobic amino acids are on the inside. Mutations that make the protein surface more soluble disrupt its folding, so the cleansing option eliminates them if they are present in solo proteins.

If the protein undergoes multiplication, however, these hydrophobic amino acids are hidden from the water at the interface surface and become invisible for cleaning. The multimer then takes root, as returning to the single state will reveal the now oil-soluble harmful interface.

This “hydrophobic shower” seems to be universal. The researchers analyzed a massive database of protein structures, including hundreds of applicants և adjacent solo proteins, and found that the vast majority of interfaces had become so hydrophobic that the dimeric egg was deeply ingrained.

Working on thousands of proteins for thousands of millions of years, this mechanism can lead to the gradual accumulation of many useless complexes inside cells.

“Some complexes, of course, have important functions, but even they will be encouraged by hydrophobic straw, which makes it harder for them to lose than it would otherwise be,” said Hochberg. “When the knife is constantly running in the background, our cells have probably accumulated a huge supply of entrenched complexes, many of which have never performed a useful function, or have long since ceased to do so.”

Future directions include exploring whether interactions other than multimerization can be the result of eradication. “It was a story about proteins darkening with their other examples, which is a very common process,” Thornton said. “But there are many other interactions in cells. We think some of them may have accumulated during evolution because of a similarly acquired dependence on molecular complexity.”

Reference. Georg KA Hochberg, Ian Liu, Eric G. Marklund, Brian P.H. Metzger, Arthur Laganovsky և Joseph ozef V. Thornton. “Hydrophobic Rachet Roots Molecular Complexes”, 2020 December 9, Nature:,
DOI: 10.1038 / s41586-020-3021-2:

A study on “Hydrophobic Rachet Roots Molecular Complexes” conducted by the Chicago Scholars: National Institutes of Health (R01GM131128 և R01GM121931). Additional authors include Brian P.H., University of Chicago. Metzger, Ian Liu և Arthur Laganowski of Texas A&M University, իկ Eric G. Marklund from Uppsala University.

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