Science, Vol 268, Issue 5211, 702-705
Copyright © 1995 by American Association for the Advancement of Science
Prebiotic synthesis of 5-substituted uracils: a bridge between the RNA world and the DNA-protein world
MP Robertson
and
SL Miller
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla 92093, USA.
Under prebiotic conditions, formaldehyde adds to uracil at the C-5 position to produce 5-hydroxymethyluracil with favorable rates and equilibria. Hydroxymethyluracil adds a variety of nucleophiles, such as ammonia, glycine, guanidine, hydrogen sulfide, hydrogen cyanide, imidazole, indole, and phenol, to give 5-substituted uracils with the side chains of most of the 20 amino acids in proteins. These reactions are sufficiently robust that, if uracil had been present on the primitive Earth, then these substituted uracils would also have been present. The ribozymes of the RNA world would have included many of the functional groups found in proteins today, and their catalytic activities may have been considerably greater than presently assumed.
