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  • Title: Cytosine 73 is a discriminator nucleotide in vivo for histidyl-tRNA in Escherichia coli.
    Author: Yan W, Francklyn C.
    Journal: J Biol Chem; 1994 Apr 01; 269(13):10022-7. PubMed ID: 8144499.
    Abstract:
    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.
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