A model for the coevolution of the genetic code and the process of protein synthesis: Review and assessment

Abstract

The contemporary genetic code and the process of protein biosynthesis most assuredly evolved from a simpler code and process. We believe that there was obligatory coevolution of the two and that the earlier code and process must have involved a more direct linkage between the amino acids and the information macromolecule. We propose that an early form of translating existed in which amino acids were attached directly to the 'messenger' RNA along the backbone as 2'OH aminoacyl esters. These esters then condensed with each other on the RNA backbone yielding a peptide covalently attached to the RNA, without the use of tRNA's and ribosomes. THis presentation is concerned with experimental data which indicate that such a simple translation system is possible and must have involved the following steps: (1) formation of the aminoacyl adenylate anhydride, (2) transfer of the amino acid from the adenylate to immidazole, (3) transfer of the amino acid from imidazole to 2'OH groups along the backbone of RNAs, (4) condensation of the amino acids to yield peptides. Steps (1)-(3) have been confirmed in chemical systems. Our preliminary evidence indicates step (4) is also possible. The aminoacylation of polyribonucleotides and the subsequent formation of peptides is a dynamic and experimentally accessible system for studying genetic coding specfities and our present studies are now concentrated on step (4), looking for such specifities.

Stereochemical Recognition in Nucleic Acid-Amino Acid Interactions and its Implications in Biological Coding: A Model Approach

“…The idea of stereochemical interaction of amino acids and their codons or anticodons has been historically one of considerable interest and debate [6,[8][9][10][11][12][13][28][29][30][31][32][33][34][35][36][37][38][39][40]. We have decided to set forth our concepts at this time to provide a working hypothesis to stimulate experiments to critically evaluate its validity.…”

From the Prebiotic Synthesis of α-Amino Acids Towards a Primitive Translation Apparatus for the Synthesis of Peptides

“…There is a last possibility to circumvent the above-mentioned difficulties; it is that life arose from an early symbiosis between amino acid/peptide and nucleotide/RNA chemistries [21][22][23][24]. It is consistent with the fact that the translation machinery (ribosome, tRNAs) seems to be one of the oldest components of the cell as a result of the universality of the genetic code.…”

Enhancement of peptide bond formation by polyribonucleotides on clay surfaces in fluctuating environments

“…These include the drastic falloff in yield as the ratio of polynucleotide to glycine increases to 1:1 or greater, and the plateau as histidyl-histidine levels are increased (White and Erickson 1980). Effect of poly A on percent yield of glycine in oligo- The mechanism of the enhancement of peptide bond formation by polyribonucleotides on clay surfaces may be similar to that proposed for reaction in aqueous solution by Lacey and Fox (1972), and supported experimentally by Lacey et al (1975). We propose that amino acids, activated by the clay, form ester bonds to 2'-OH positions of ribose units in the polyribonucleotides followed by attack on the ester of one amino acid by the amino group of an adjacent amino acid ester (Fig.…”

“…Furthermore, some selectivity of amino acids in relation to the base residues at the site of attachment was apparently observed. This work is further discussed by Woese (1967) and Lacey et al (1975).…”