CODING COENZYME HANDLES - A HYPOTHESIS FOR THE ORIGIN OF THE GENETIC-CODE

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.