Functional compensation of a recognition-defective transfer RNA by a distal base pair substitution.
A single G3:U70 base pair in the acceptor helix is the major determinant of alanine acceptance in alanine transfer RNAs. Transfer of this base pair into other transfer RNAs confers alanine acceptance. A G3:C70 substitution eliminates alanine acceptance in vivo and in vitro. In this work, a population of mutagenized G3:C70 alanine tRNA amber suppressors was subjected to a selection for mutations that compensate for the inactivating G3:C70 substitution. No compensatory mutations located in the acceptor helix were obtained. Instead, a U27:U43 substitution that replaced the wild-type C27:G43 in the anticodon stem created a U27:U43/G3:C70 mutant alanine tRNA that inserts alanine at amber codons in vivo. The U27:U43 substitution is at a location where previous footprinting work established an RNA-protein contact. Thus, this mutation may act by functionally coupling a distal part of the tRNA structure to the active site.
Hou
Y M
YM
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Schimmel
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D000595:Amino Acid Sequence; D000926:Anticodon / Q000235:genetics; D001482:Base Composition; D001483:Base Sequence; D003062:Codon / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D005813:Genes, Synthetic; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009690:Nucleic Acid Conformation; D010641:Phenotype; D012344:RNA, Transfer, Ala / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D013489:Suppression, Genetic; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics
D000926:Anticodon; D003062:Codon; D012344:RNA, Transfer, Ala; D013762:Tetrahydrofolate Dehydrogenase