At the most basic level, any organism is an area separated from the surrounding space in which metabolic processes take place. It was with such protocells that life began on Earth more than three and a half billion years ago. Of course, they were extremely primitive, but they could carry out key metabolic reactions that provided them with energy, the ability to reproduce, and the like.
It is believed that one of these reactions was the oxidation of hydrogen. There was much more of it on the young Earth than today, and it could well serve as a source of energy for newborn life. Some bacteria and archaea still use hydrogen for this purpose today, oxidizing it with oxygen, sulfate, carbon dioxide, and other suitable substances. These reactions are catalyzed by enzymes. hydrogenase.
Most likely, the precursor molecules of hydrogenases were also present in the very first protocells. But if in modern microbes these are large, complex proteins containing hundreds of amino acids and various cofactors, then at the dawn of life they were arranged much simpler. A team of scientists from Rutgers University managed to determine such a “minimal hydrogenase”. Their article published In the magazine Science Advances.
Vikas Nanda’s laboratory is a key site for a massive research project ENIGMA, whose participants are trying to determine the “minimal set of minimal proteins” that can provide a transition from prebiotic reactions to real biology and the emergence of life. To find such a hydrogenase, scientists analyzed the structures of enzymes that exist today and carried out computer simulations, ridding them of “all that is superfluous.”
As a result, they obtained a short peptide containing only 13 amino acid residues and two nickel atoms coordinated with them. The authors named this molecule Nickelback. Laboratory experiments have shown that such peptides are able to assemble spontaneously under suitable conditions, remain stable and exhibit catalytic activity in hydrogen oxidation. It is possible that complex, multicomponent proteins of modern organisms originated from such primitive molecules. But at first, young life relied on them.