Israeli scientists design prototype of 3.7-bln-year-old proteins

JERUSALEM, April 1 (Xinhua) -- Israeli scientists created a prototype of the first ancient enzymes, concluding that the first cellular life, about 3.7 billion years ago, consisted of DNA and RNA molecules, Weizmann Institute of Science in the center of the state reported on Monday.

According to the research published in the journal Proceedings of the American Academy of Sciences, DNA and RNA molecules were responsible in the ancient cells for the actions currently reserved for enzymes.

The researchers said that the first proteins were probably multi-functional and simple, and as evolution progressed, they turned into efficient and unique enzymes.

They noted that the enzyme's phosphate-binding loops (p-loops) was a possible starting point to produce a prototype of the ancient enzyme.

Enzymes pluck phosphates off Adenosine Triphosphate molecule to use in the various biochemical reactions they implement.

These reactions mainly involve attaching the phosphate groups to other metabolites like sugars, and activating them.

Thus, the p-loop, which carries and releases the phosphate group, is essential to the functioning of almost all living cell systems.

The researchers used the sequences of modern p-loop-based proteins to infer the oldest p-loop sequence, and then designed brand new protein sequences to contain this ancient loop.

"The fact that these small proteins worked so well to help to understand how enzymes could have started from short sequences," researchers said.

The surprise was that the p-loops in the designed enzymes not only bound ATP but also bound strongly to DNA and RNA, reinforcing the scenario that the source of life is in DNA and RNA molecules.