Volcanic gas activates amino acids
03 October 2005
The volcanic gas carbonyl sulfide (COS) might have triggered a key step in the origin of life by chemically activating amino acids.
Work by John Sutherland's group at the University of Manchester, UK follows that by Reza Ghadiri and colleagues at the Scripps Research Institute in La Jolla, California, US. Ghadiri recently showed that COS reacts with amino acids to form a thiocarbamate, which then rearranges into a circular N-carboxyanhydride (NCA). This species represents an activated amino acid, which readily reacts with other amino acids to form peptides.1
Sutherland has now expanded the repertoire of NCAs by showing that they also react with ribonucleotides, forming an ester bond analogous to that in biochemically activated amino acids, the aminoacyl-tRNA complex.2
Researchers investigating the origin of life see the protein synthesis apparatus - made mostly of RNA - as the key to the start of the so-called division of labour between nucleic acids and proteins.
The coupling of amino acids to specific nucleotides of specific tRNAs is a key event in this context. 'Today, protein enzymes carry out this coupling, but at the time when evolution only started to develop peptide synthesis, a chemical mechanism must have brought together amino acids and nucleotides,' said Kevin Plaxco from the University of California at Santa Barbara. 'For this crucial chemical reaction at the crossroads of early evolution, the activation of amino acids by COS emitted by volcanoes is an interesting candidate.' Michael Gross
1 L Leman et al, Science, 2004, 306, 283.2 J-P Biron et al, Angew. Chem. Int. Ed., 2005, 44, (DOI: 10.1002/anie.200501591)