The question of how living organisms arise from non-living matter remains one of the deepest mysteries in science. Although there are many theories, conclusive explanations remain elusive. This is not surprising considering that these events took place between three and four billion years ago, under very different ancient conditions on Earth.
Over such a long period of time, evolution has completely erased traces of the origins of life," said Roland Rick, professor and associate director of the newly established Interdisciplinary Center for the Origin and Epidemiology of Life at ETH Zurich. Science has no choice but to formulate hypotheses and confirm them as thoroughly as possible with experimental data.
For years, Riek and his team have pursued the idea that protein-like aggregates, known as amyloid, may have played an important role in the transition between chemistry and biology. The first step for Riek's team was to demonstrate that this amyloid could be formed relatively easily under conditions that might have prevailed on the early Earth: in the lab, it only takes a little volcanic gas (along with experimental skill and a lot of patience) to combine simple amino acids into short peptide chains, which can then be assembled spontaneously into fibers.
Thanks to the tireless efforts of Riek's team, the self-replicating properties of amyloid were confirmed, a discovery that undoubtedly labeled it as a precursor molecule of life. Now, researchers are once again on a journey of discovery, and their latest research shows that amyloid not only binds to RNA and DNA molecules, but also relies in part on electrostatic attraction.
Over the course of their research, they found that amyloid has a positive charge in some places and a negative charge in the genetic material, especially in neutral to acidic environments. This discovery sheds light on the delicate relationship between genetic material and amyloid. In addition, Riek and his team note that this interaction does not depend solely on charge, as the sequences of RNA and DNA nucleotides also play an important role in it. The discovery suggests that they may represent an early form of the universal genetic code that binds all living things together. All in all, Riek's team has shed valuable light on the mysterious link between amyloid and genetic material through in-depth research, providing valuable clues to understanding the origin and evolution of life. However, "even though we see differences in how RNA and DNA molecules bind to amyloid, we don't yet understand what those differences mean," Riek said. Our model may still be too simple. That's why he thinks another aspect of the results is particularly important: when genetic material attaches to amyloid, both molecules gain stability. In ancient times, this increased stability may have proved to be a great advantage.
This is because, in that so-called primordial soup, the biochemical molecules are like a thin morning mist, elusive. In today's biological cells, these molecules are as dense as stars. As Riek's researchers describe in a recent article, "Amyloid has shown the potential to increase the local concentration and sequence of nucleotides in an otherwise diluted disordered system." This stark contrast, like the transition from mist to stars, reveals the wonder and greatness of biological evolution.
Rick points out that while competition is at the heart of Darwin's theory of evolution, collaboration also plays an important evolutionary role. Both classes of molecules benefit from the stable interaction between amyloid and RNA or DNA molecules, as long-lived molecules accumulate more strongly over time than labile substances. It may even be that molecular cooperation, rather than competition, is the decisive factor in the emergence of life. "After all, there may not have been a shortage of space or resources at the time," Rick said.
Reference: Saroj Krout、riccardo cadalbert、nina schr der、julia wang、johannes zehnder、olivia gampp、thomas wiegand、peter güntert、d**id klingler、christoph kreutz、anna kn rlein、jonathan hall、jason Greenwald and Roland Riek, October 2, 2023, Journal of the American Chemical Society.
doi： 10.1021/jacs.3c06287