Is this how life emerged from stuff that was anything but alive?
How life crawled out of primordial ooze is a mystery literally as old as Earth itself. There must have been something that switched on the transition from inanimate to alive — but what?
What life even is might be the better question. There could be extraterrestrial life-forms out there which could change our entire idea of what it means to be a living thing (and we might not even recognize them). Before anything lived on Earth, it was a mess of proteins and other potential ingredients for life, some of which ended up creating the first microorganisms which kept evolving and diversifying and re-evolving into everything from single-celled algae to dinosaurs.
For us Earthlings, being alive means the ability to capture energy and put it to use, at least if you ask researcher Yana Bromberg of Rutgers University, who recently led a study published in Science Advances. She and her team were trying to figure out what might have turned life on billions of years ago when they realized that there was a real possibility in proteins that could bind metals. Something that used those proteins might have been the first forms of life.
“All biotic activities, like the cellular functions that are necessary for life, require acquiring, using, and storing energy,” she told SYFY WIRE. “For this, electrons need to be moved around. Thus, any first ‘life’ would need to be able to handle electron transfer.”
Metal-binding proteins can bind metal ions for different purposes. Some of these proteins are stabilized by these ions, while others use them to regulate cell processes in different ways. Then there are proteins which bind to metals which are able to catalyze. Catalysis is the process that accelerates chemical reactions and is important for life. Remember that. Bromberg and her team went through all the existing metal-binding proteins to see what they had in common, because that could lead to their ancestors which might have been around on nascent Earth.
The researchers found that most of the proteins they compared have similar cores that bind metal, no matter what metal it is that they bind themselves to, even if the actual proteins were nothing alike. Substructures in these cores tend to keep repeating themselves and were curiously observed in other parts of the proteins and proteins that do not bind metal. This may not sound like much, but what it revealed was that the vast range of proteins and protein functions which now exist must have emerged from no more than a few common ancestors.
Translation: the ancestral proteins had the potential to bring about what we know as life.
“There was a small number of ways (or even just a single one) of using peptides for metal binding for electron transfer,” said Bromberg. “This original peptide may have been then reproduced and diversified to provide for the set of metal binding functions we currently observe.”
Proteins are made of peptides, which are made of amino acids. Amino acids are necessary for life but can exist outside of living organisms. Whenever these organic compounds are found somewhere else besides Earth, it goes viral, because aliens, but organics do not necessarily mean life is there, though the inverse is true: the presence of life means organics. We still have no idea how life spawned out of nowhere. What went into creating living things out of abiotic substances is unknown, but this can give us further insight into what might have happened.
Another thing Bromberg’s study could help with is what to search for as we keep scouring the universe for signs of life. There are plenty of organics out there, which may or may not be indicators that something is creeping around on a faraway exoplanet. Alien life-forms continue to elude us. If we can go way back and get some idea of how life may have emerged on early Earth, and what that might have looked like, it can at least help astrobiologists identify a planet on which life is just starting to open its eyes, whether or not it actually has them.
“If we can identify similar peptides elsewhere, this would indicate that life may appear (or previously existed) where we see them,” Bromberg said. “Our findings also provide a new direction for understanding the appearance of life on Earth, which may apply to other planets.”
