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tadA, an essential tRNA‐specific adenosine deaminase from Escherichia coli
Author(s) -
Wolf Jeannette,
Gerber André P.,
Keller Walter
Publication year - 2002
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdf362
Subject(s) - transfer rna , biology , wobble base pair , biochemistry , inosine , escherichia coli , yeast , saccharomyces cerevisiae , rna , genetics , enzyme , gene
We report the characterization of tadA, the first prokaryotic RNA editing enzyme to be identified. Escherichia coli tadA displays sequence similarity to the yeast tRNA deaminase subunit Tad2p. Recom binant tadA protein forms homodimers and is sufficient for site‐specific inosine formation at the wobble position (position 34) of tRNA Arg2 , the only tRNA having this modification in prokaryotes. With the exception of yeast tRNA Arg , no other eukaryotic tRNA substrates were found to be modified by tadA. How ever, an artificial yeast tRNA Asp , which carries the anticodon loop of yeast tRNA Arg , is bound and modified by tadA. Moreover, a tRNA Arg2 minisubstrate containing the anticodon stem and loop is sufficient for specific deamination by tadA. We show that nucleotides at positions 33–36 are sufficient for inosine formation in mutant Arg2 minisubstrates. The anticodon is thus a major determinant for tadA substrate specificity. Finally, we show that tadA is an essential gene in E.coli , underscoring the critical function of inosine at the wobble position in prokaryotes.