Amino acids: Why are the building blocks of life left-handed?

One of life’s greatest riddles, so-called homochirality, life’s preference for “left-handed” amino acidsIt was the subject of a recent study funded by NASA. However, the discovery that this special feature may not be the result of chemical determinism deepened the mystery even further.

Amino acids, a kind of building blocks of life, can exist in two forms: left-handed (levorotator, or L) and right-handed (dexterous, or D). However, it is clear that all amino acids used by living things in nature act in the L form, that is, the L-amino acids in proteins and the D form of sugars in nucleic acid structures.

The research, published in the journal Nature Communications, shows that before DNA existed, RNA, a molecule that could be a carrier of genetic information, Can produce both left- and right-handed amino acids. The discovery refutes the thesis of chemical determinism and a specific molecular orientation in the origin of life.

Hypothesis of an RNA world at the origin of life

The researchers tested the hypothesis that RNA, a molecule “externally supplied” by DNA to carry instructions to protein-building ribosomes, was originally responsible for this type of left-handed rather than right-handed protein structure. It’s become a secret now because life based on right-handed amino acids would theoretically function well.

To simulate potential conditions on early Earth, the authors introduced RNA molecules that function as enzymes, a characteristic function of proteins but an unusual function for a nucleotide molecule. RNA molecules that act as enzymes form amino acids called ribozymes.

According to corresponding author Irene Chen, a scientist at the University of California, Los Angeles (UCLA), “The experiment showed that ribozymes can prefer left- or right-handed amino acids, indicating that RNA worlds in general will not necessarily change. Currently in biology “We have a strong bias towards the form of amino acids we observe.”

The “fault” of homochirality is not RNA

According to co-author Alberto Vázquez-Salazar, a postdoctoral researcher at UCLA, “The findings show that: that the ultimate homochirality of life may not have been the result of chemical determinism but arose through later evolutionary pressures.“.

He specifically mentions the building blocks of life (amino acids) brought by asteroids during Earth’s prebiotic history, whose fossil records were erased by plate tectonics.

While we can’t come to a definitive conclusion about homochirality, understanding the chemical properties of life provides useful clues for NASA “to know what to look for in our search for life in the solar system,” said co-author Jason Dworkin of the Goddard Space Flight Center. .

Stay up to date with the latest astrobiology studies at TecMundo. If you wish, take the opportunity to share the article with your friends on social media. Until later!