On the origin of the genetic code Eörs Szathmáry Collegium Budapest Eötvös University

The structure of the genetic code

Variants of the common code

Amino acid biosynthesis in E. coli

Coevolution chart Precursor-product pairs in biosynthesis Dashed boxes are hypothetical intermediate stages Italicised codons do not match coevolution predictions

Constraints on codon reshuffling for statistical investigations

3 ways of code evolution

Forces may have changed in strength

Cofactor use by aptamers

From RNA to protein Gradual lose of scaffold Amino acids to peptides to proteins Not very well worked out

Piecewise evolution of tRNA

Proteins from pieces

Superfolds

Some more proteins

Ribosomal proteins cannot fold by themselves

Tryptophan-binding aptamers

The smallest typtophan binder The anticodon is CCA 13 fully conserved nucleotides (26 bits of information) Selective among hydrophobic changes

An interesting idea? First two bases of a codon implied in synthesis of amino acids originating from the reductive citric acid cycle