The question of how life began on our planet is still being answered, but a new study identifies the structures of the proteins that may have made it happen.
The team behind the study decided to start from the premise that life depends on collecting and using energy. In the primordial soup of ancient Earth, that energy would most likely have come from the skies, in the shape of radiation from the Sun, or from deep within Earth itself.
The transfer of electrons is a fundamental chemical process which involves an electron moving from one atom to another. Some of the basic functions of life are dependent on electron transfer.
The researchers decided to combine metals and the complex molecule called proteins, which are what drives most biological processes, to search for metals that bind to the complex molecule.
A methodical, computational approach was used to compare metal-finding proteins, revealing certain common features that matched across all of them.
"We saw that the metal-binding core of the existing proteins are similar even though the proteins themselves may not be," says microbiologistYana Bromberg from Rutgers University-NewBrunswick in New Jersey.
The metal-binding cores are often made up of repeated substructures, like Lego blocks. These blocks were found in other regions of the proteins, not just metal-binding core, and many other other other proteins that were not considered in our study.
The researchers suggest that these shared features may have been present in the earliest proteins and that they may have changed over time to become the proteins we see today.
The Archean Ocean that covered Earth thousands of millions of years ago could have been used to power the electron shuffling needed for energy transfer and, in turn, biological life.
"Our observation suggests that these little building blocks may have had a single or a small number of common ancestors and given rise to the whole range of proteins and their functions that are currently available," says Bromberg. "That is to life as we know it."
The team was able to identify evolutions in the shapes of the folds of the proteins that may have produced the proteins we know today.
The study concludes that biologically functional peptides, the smaller versions of the same proteins, may have been predated by the earliest ones. This adds to our understanding of how life began.
Any analysis of the beginnings of life on Earth can be important in looking for life on other planets, where life might have already evolved along similar biological paths.
We don't have a lot of information about how life arose on this planet, and our work contributes a previously unavailable explanation.
"Our finding of the specific structural building blocks is related to synthetic biology efforts, where scientists aim to construct specifically active proteins anew."
Science Advances has published the research.