Cytosine 73 is a discriminator nucleotide in vivo for histidyl-tRNA in Escherichia coli.
The acceptor helix of histidine tRNAs in Escherichia coli is capped by a unique base pair in which the cytosine at the discriminator position is paired with an extra guanosine at -1. In previous in vitro studies, the presence of the G-1:C73 base pair was found to be required to obtain both optimal histidylation by histidyl-tRNA synthetase and accurate 5' processing by RNase P. We investigated the role of G-1:C73 in histidine tRNA identity and found that nucleotide substitutions conferred mischarging by other amino acids in a pattern that correlated with the discriminator base and not with the extra nucleotide at -1. As shown by primer extension experiments, the relatively minor role of the -1 nucleotide in vivo could be attributed to altered RNase P processing. These studies show that interactions of tRNAs in vivo both with RNase P during tRNA biosynthesis and with the pool of aminoacyl-tRNA synthetases can modulate the effects of substitutions at recognition nucleotides, eliciting changes in transfer RNA identity.
Yan
W
W
Department of Biochemistry, University of Vermont College of Medicine, Burlington 05405.
Francklyn
C
C
D001482:Base Composition; D001483:Base Sequence; D003596:Cytosine; D017931:DNA Primers; D004926:Escherichia coli / Q000378:metabolism*; D005798:Genes, Bacterial; D016153:Genes, Suppressor; D006643:Histidine-tRNA Ligase / Q000378:metabolism*; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides; D012354:RNA, Transfer, His / Q000235:genetics* / Q000378:metabolism*; D013489:Suppression, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis
D017931:DNA Primers; D009838:Oligodeoxyribonucleotides; D012354:RNA, Transfer, His; D003596:Cytosine; D001616:beta-Galactosidase; D006643:Histidine-tRNA Ligase