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PubMed1965

The genetic code.

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Genetic Code↗
PubMed1995

Specific aminoacylation of C4N hairpin RNAs with the cognate aminoacyl-adenylates in the presence of a dipeptide: origin of the genetic code.

A series of C4N hairpin RNAs bearing anticodon nucleotides at the 5' ends and a discriminator base and the sequence CCA at the 3' ends was constructed by an in vitro transcription system using T7 RNA polymerase. These RNAs were aminoacylated specifically with their cognate amino acids by reaction with aminoacyl-adenylates in the presence of a dipeptide, valyl-aspartic acid, suggesting that such hairpin RNAs are able to play the role of the present-day tRNA and that valyl-aspartic acid can perform the function of the present-day aminoacyl-tRNA synthetase as a catalyst in the aminoacylation reaction. These results should provide a useful clue to elucidating the origin of the genetic code.

Adenosine Monophosphate↗
PubMed1985

A multivariate study of the relationship between the genetic code and the physical-chemical properties of amino acids.

The 20 naturally occurring amino acids are characterized by 20 variables: pKNH2, pKCOOH, pI, molecular weight, substituent van der Waals volume, seven 1H and 13C nuclear magnetic resonance shift variables, and eight hydrophobicity-hydrophilicity scales. The 20-dimensional data set is reduced to a few new dimensions by principal components analysis. The three first principal components reveal relationships between the properties of the amino acids and the genetic code. Thus the amino acids coded for by adenosine (A), uracil (U), or cytosine (C) in their second codon position (corresponding to U, A, or G in the second anticodon position) are grouped in these components. No grouping was detected for the amino acids coded for by guanine (G) in the second codon position (corresponding to C in the second anticodon position). The results show that a relationship exists between the physical-chemical properties of the amino acids and which of the A (U), U (A), or C (G) nucleotide is used in the second codon (anticodon) position. The amino acids coded for by G (C) in the second codon (anticodon) position do not participate in this relationship.

Amino Acids↗
PubMed1987

Hydrogen bonding between cytosine and peptides of threonine or serine: is it relevant to the origin of the genetic code?

13C, 15N, and 1H nuclear magnetic resonance measurements indicate that chloroform-soluble threonine-containing tripeptide derivatives, such as t-Boc-Thr-Gly-Gly-OBz, form three strong hydrogen bonds to the cytosine moiety of 2',3'-O-isopropylidene-5'-O-t-butyldimethylsilylcytidine. The C = O and NH of the central peptide residue plus the OH of the threonine side chain appear to form bonds to the N(4')H2, N(3), and C(2) = O, respectively, of the pyrimidine. An association constant calculated from the cytidine 15N(4') nuclear magnetic resonance response to added peptide is four times larger than the corresponding cytosine-guanine constant. It is suggested that cytosine-peptide bonding was part of the primitive genetic coding mechanism early in evolution and accounts for the origin of the cytosine-centered codons for the hydroxy amino acids, serine and threonine, in the present code.

Codon↗
PubMed1981

On the origin of biological systems and the role of poly-nucleotides -- the initiation of evolution, the structural basis of the genetic code and the mechanism of protein biosynthesis.

There is much information on the nature and function of biological systems in the structures of the small molecules that affect them and in the biosynthetic and other reactions in which they are involved. Combining this with biochemical and polynucleotide sequence information allows us to derive explanations for a number of biological problems that earlier were unclear or even quite obscure. Thus polynucleotide systems give a good account of the origin of life, of the genetic code and of the function of the ribosomal mechanism of protein biosynthesis. It is apparent that polynucleotides play a more important role than has been fully appreciated.

Biological Evolution↗
PubMed1982

Globular proteins, GU wobbling, and the evolution of the genetic code.

It has previously been shown that the formation of GU base pairs in RNA copying processes leads to an accumulation of G and U in both strands of the replicating RNA, which results in a non-random distribution of base triplets. In the present paper, this distribution is calculated, and, using the X2-test, a correlation between the distribution of triplets and the amino acid composition of the evolutionarily conservative interior regions of selected globular proteins is established. It is suggested that GU wobbling in early replication of RNA could have led to the observed amino acid composition of present-day protein interiors. If this hypothesis is correct, then GU wobbling must have been very extensive in the imprecisely replicating RNA, even reaching values close to the critical for stability of its double-helical structure. Implications of the hypothesis both for the evolution of the genetic code and of proteins are discussed.

Biological Evolution↗