Why are all proteins ‘left-handed’? New theory could solve origin of life mystery

There’s a bias at the heart of life, and its origin is an enduring mystery. Nearly all the amino acid building blocks of proteins today exist in mirror-image forms, like right- and left-handed gloves. But life only uses left-handed ones, even though both forms should have been equally abundant during the planet’s early days and can readily link up in the lab. Something must have tipped the balance toward lefties in the primordial soup and preserved the bias ever since. Now, a trio of U.S. researchers proposes a novel explanation. Today in Nature , they report that by monitoring the formation rates of amino acid pairs, called dipeptides, they’ve found multiple mechanisms that ultimately promote dipeptides whose two members share the same handedness. “It’s quite convincing,” says Gerald Joyce, a pioneering origin of life chemist and president of the Salk Institute for Biological Studies who was not involved with the study. Researchers next hope to learn whether the same mechanisms skew larger peptides and proteins toward left-handedness—and whether it can explain the opposite bias in RNA and DNA, whose bases have sugars that are inevitably right-handed. If so, the new mechanisms could explain how life itself took on one mirror-image form and not the other. Several explanations have been advanced in recent decades for life’s chirality, as the bias toward a particular handedness is known. For example, meteorites, which could have seeded...
Source: Science of Aging Knowledge Environment - Category: Geriatrics Source Type: research