RNA minihelices and the decoding of genetic information.
The rules of the genetic code are determined by the specific aminoacylation of transfer RNAs by aminoacyl transfer RNA synthetase. A straightforward analysis shows that a system of synthetase-tRNA interactions that relies on anticodons for specificity could, in principle, enable most synthetases to distinguish their cognate tRNA isoacceptors from all others. Although the anticodons of some tRNAs are recognition sites for the cognate aminoacyl tRNA synthetases, for other synthetases the anticodon is dispensable for specific aminoacylation. In particular, alanine and histidine tRNA synthetases aminoacylate small RNA minihelices that reconstruct the part of their cognate tRNAs that is proximate to the amino acid attachment site. Helices with as few as six base pairs can be efficiently aminoacylated. The specificity of aminoacylation is determined by a few nucleotides and can be converted from one amino acid to another by the change of only a few nucleotides. These findings suggest that, for a subgroup of the synthetases, there is a distinct code in the acceptor helix of transfer RNAs that determines aminoacylation specificity.
Schimmel
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Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
D000604:Amino Acyl-tRNA Synthetases / Q000502:physiology; D000926:Anticodon / Q000502:physiology; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000502:physiology*; D013379:Substrate Specificity
D000926:Anticodon; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases