E. Szathmary, CODING COENZYME HANDLES - A HYPOTHESIS FOR THE ORIGIN OF THE GENETIC-CODE, Proceedings of the National Academy of Sciences of the United Statesof America, 90(21), 1993, pp. 9916-9920
The coding coenzyme handle hypothesis suggests that useful coding prec
eded translation. Early adapters, the ancestors of present-day anticod
ons, were charged with amino acids acting as coenzymes of ribozymes in
a metabolically complex RNA world. The ancestral aminoacyl-adapter sy
nthetases could have been similar to present-day self-splicing tRNA in
trons. A codon-anticodon-discriminator base complex embedded in these
synthetases could have played an important role in amino acid recognit
ion. Extension of the genetic code proceeded through the takeover of n
onsense codons by novel amino acids, related to already coded ones eit
her through precursor-product relationship or physicochemical similari
ty. The hypothesis is open for experimental tests.