ISSN:
1617-4623
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Previous studies have demonstrated many amino acid and codon substitutions at position 211 of the alpha chain of tryptophan synthetase of Escherichia coli. In order to extend our studies on suppressor tRNAs and, in general, on accuracy in the translation of genetic information, we have devised specific selections for sense and nonsense codons corresponding to alpha chain position 234. Using codon-specific suppressors and selection for missense revertants of nonsense mutations, we have brought to 18 (from six) the number of codons at 234. This number includes all three nonsense codons and ten (of the remaining 15) that code for nonfunctional amino acids at that position. Furthermore, by adding to these results the testing of the suppressibility of trpA(234) nonsense mutations by suppressor tRNAs of known aminoacylation specificity, we have increased to 12 (from five) the number of amino acids whose functionality at position 234 is known. The existence of trpA mutants with so many amino acid substitutions at two positions in the tryptophan synthetase alpha chain should prove helpful for structure-function studies of that protein. Furthermore, the availability, at both positions, of at least 12 condons (including the three nonsense codons) that result in a nonfunctional alpha chain allows the selection of mutations that affect the suppression of a given codon as it occurs in two different mRNA contexts. Studies with such mutants should help elucidate the role in translational accuracy of mRNA secondary structure, tRNA-tRNA interactions on the ribosome, and interactions of the ribosome with tRNA, mRNA, and, in the case of nonsense suppression, peptidyl release factors.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00330900
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