(ORDO NEWS) — The question of how life first began on our planet has not yet been fully answered, but science is constantly approaching it, and a new study has identified the protein structures that could make it happen.
To begin with, the research team decided to assume that life as we know it depends on the collection and use of energy. In the primordial soup of ancient Earth, this energy most likely came from the sky as radiation from the Sun, or from deep within the Earth itself as heat seeping through hydrothermal vents at the bottom of ancient seas.
At the molecular level, the use of energy means the transfer of electrons – the fundamental chemical process in which an electron moves from one atom or molecule to another. Electron transfer is at the heart of redox reactions (also known as redox reactions), which are vital to some of the basic functions of life.
Since metals are the best elements for electron transport, and complex molecules called proteins are the driving force behind most biological processes, the researchers decided to combine the two and find proteins that bind metals.
A methodical, computational approach was used to compare metal-binding proteins, revealing certain commonalities that were shared by all of them – regardless of the functionality of the protein, the metal it binds to, or the organism.
“We saw that the metal-binding cores of existing proteins are indeed similar, even if the proteins themselves are not similar,” says microbiologist Jana Bromberg of Rutgers University New Brunswick in New Jersey.
We also saw that these metal-binding cores are often made up of repeating Lego-like substructures. Curiously, these blocks were also found in other regions of proteins, not only in metal-binding nuclei, and in many other proteins that were not considered in our study.”
These common features may well have been present and working in the earliest proteins, the researchers suggest, changing over time to become the proteins we see today – but retaining certain common structures.
It is hypothesized that the soluble metals in the Archean ocean that covered the Earth thousands of millions of years ago could have been used to transfer energy and, in turn, for biological life.
“Our observation suggests that rearrangements of these small building blocks could have had one or a small number of common ancestors and lead to the full range of proteins and their functions that exist today,” says Bromberg. “That is, to life as we know it.”
In particular, the team was able to identify the evolution of protein folds – the shapes that proteins take when they become biologically active – that could lead to the proteins we know today, almost like a blueprint for a molecular family tree.
The study also concludes that biologically functional peptides, smaller versions of proteins, may have existed even before the earliest proteins, which arose 3.8 billion years ago. All this expands our understanding of how life began.
As always, any analysis of the origin of life on Earth can be important in the search for life on other planets, where life can begin to develop (or has already developed) along similar biological paths.
“We have very little information about how life arose on our planet, and our work provides an explanation that was not previously available,” says Bromberg. “This explanation could also potentially contribute to our search for life on other planets and planetary bodies.”
“Our finding of specific structural building blocks could also have implications for synthetic biology, where scientists are looking to re-create specifically active proteins.”
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