Chemists say they have solved a crucial problem in a theory of life’s beginnings, by demonstrating that RNA molecules can link short chains of amino acids together.
The findings, published on 11 May in Nature, support a variation on the ‘RNA world’ hypothesis, which proposes that before the evolution of DNA and the proteins it encodes, the first organisms were based on strands of RNA, a molecule that can both store genetic information — as sequences of the nucleosides A, C, G and U — and act as a catalyst for chemical reactions.
The discovery “opens up vast and fundamentally new avenues of pursuit for early chemical evolution”, says Bill Martin, who studies molecular evolution at Heinrich Heine University Düsseldorf in Germany.
In an RNA world, the standard theory says, life could have existed as complex proto-RNA strands that were able to both copy themselves and compete with other strands. Later, these ‘RNA enzymes’ could have evolved the ability to build proteins and ultimately to transfer their genetic information into more-stable DNA. Exactly how this could happen was an open question, partly because catalysts made of RNA alone are much less efficient than the protein-based enzymes found in all living cells today. “Although [RNA] catalysts were discovered, their catalytic power is lousy,” says Thomas Carell, an organic chemist at Ludwig Maximilian University of Munich in Germany. [Continue reading…]