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At least 811 records · Page 45Linked to original sources
PubMed2000

Physico-chemical constraints connected with the coding properties of the genetic system.

New insights on the origin of the genetic code, based on the analysis of the physico-chemical properties of its molecular constituents (RNA and amino acids), are reported in this paper. We point out a symmetry in the genetic code table and show that it can be explained by the nature of the anticodon-codon interaction. The importance of the strength of this interaction is examined and a correlation is found between the free-energy change (DeltaG(0)) of anticodon-codon association and the volume of the corresponding amino acids. This correlation is investigated in conjunction with the well-known one linking the hydrophobicity of the anticodons with that of the amino acids. We show that they can be considerated separately and that the energy vs. volume correlation may be explained by the process implicating the peptide bond formation between two successive amino acids during translation. This interpretation is supported by a statistical pattern of bases (purines or pyrimidines), observed in present coding genes, and by considerations involving the availability of the different kinds of amino acids. Finally, we try to explain the hydrophobicity correlation when reconstructing the events at the time of the so-called "RNA World". The whole of our investigation shows that the genetic code might be sufficiently robust to exist without the participation of pre-existing proteins, and that this robustness is a consequence of the physico-chemical properties of the four bases of the genetic system.

Amino Acids↗
PubMed1983

Changes in the amino acid code.

The genetic code is characterized by a pattern arising from "wobble-pairing" between codons and anticodons, so that one nucleotide in the first anticodon position can pair with more than one nucleotide in the third position of a codon. Earlier codes may have existed in which there were fewer anticodons than at present, so that these earlier codes contained fewer amino acids. The universal code was formerly thought to be the only currently existing code used by terrestrial species. It is now known that differences exist from the universal code in mitochondrial coding systems, and also that mitochondrial systems differ from each other. These findings lend support to the proposal that archetypal codes preceded the present universal code. Such archetypal codes may have had some resemblances to mitochondrial codes.

Amino Acids↗
PubMed1993

The genetic code-function and evolution.

The genetic code is reviewed from the standpoints of its function and evolution. The code has probably always consisted of 64 units (codons), each containing three bases. Each codon pairs with a three-base anticodon that is part of an adaptor molecule. The adaptors are transfer RNA molecules that are each joined to a specific amino acid. Many departures from the universal code have recently been discovered. These are discussed.

Amino Acids↗
PubMed2002

Specific interactions between sense and complementary peptides: the basis for the proteomic code.

The discovery of the genetic code was one of the milestone events in biology: a conserved, universal code defining the primary amino acid sequences of all proteins of all organisms. However, this code has been thought to be limited, unable to provide additional information appropriate to defining the three-dimensional structure and function of these proteins. This raises important questions. Can there be more to the genetic code? Is there a code embedded within the code? Does a two-dimensional genetic code exist? In our view, the answer to all three of these questions is a qualified "yes". This review describes how sense and complementary peptides coded for by mutually complementary nucleic acid sequences are capable of interacting specifically, thereby suggesting the existence of a second, two-dimensional genetic code (proteomic code). Theories attempting to explain such specific interactions between sense and complementary peptides are discussed including the Mekler-Idlis (M-I) pair theory that suggests that each codon-directed amino acid residue in a sense peptide may make a specific pair-wise interaction with the corresponding complementary codon-directed residue in the complementary peptide. In effect, through-space interactions between pairs of amino acid residues are suggested as being specified by the genetic code and its complement. The biological implications of sense/complementary peptide interactions are potentially vast but still to be fully understood and appreciated. That such peptide/peptide interactions could provide the basis for understanding and constructing the proteomic code remains to be properly established but research to date suggests that we should be able to make a start in that direction.

Amino Acids↗