Oct 1, 1972

Is there a discriminator site in transfer RNA?

Proceedings of the National Academy of Sciences of the United States of America
D M CrothersG Söll


We determined the nature of the fourth nucleotide from the 3'-end of several Escherichia coli tRNAs, and tabulated these results with the same data for all known tRNA sequences. We find a striking constancy of the fourth nucleotide in tRNAs specific for a given amino acid. Furthermore, tRNAs specific for chemically related amino acids are very likely to have the same nucleotide at the fourth position. One possible explanation for these regularities is the "discriminator" hypothesis: The code by which tRNA is recognized by its cognate aminoacyl-tRNA synthetase is logically hierarchical, with the fourth nucleotide serving as a primary "discriminator" site to subdivide the tRNAs into groups for recognition purposes. Each such group could have its own recognition code, or could be further subdivided by a secondary discriminator site. According to this hypothesis, chemically similar amino acids have the same discriminator nucleotide because they evolved from a single set of related amino acids indistinguishable to a primitive system. There are other possible explanations for the observed regularities at the fourth nucleotide. For example, it is conceivable that the position is used for a direct physical interaction with the amino ac...Continue Reading

  • References29
  • Citations129


  • References29
  • Citations129


Mentioned in this Paper

Alkalescens-Dispar Group
Amino Acids, I.V. solution additive
MT-TA gene
Triplet Codon-amino Acid Adaptor Activity
Chromatography, DEAE-Cellulose
Transfer RNA

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