The selenocysteine-inserting opal suppressor serine tRNA from E. coli is highly unusual in structure and modification.
Selenocysteine is cotranslationally incorporated into selenoproteins in a unique pathway involving tRNA mediated suppression of a UGA nonsense codon (1-3). The DNA sequence of the gene for this suppressor tRNA from Escherichia coli predicts unusual features of the gene product (4). We determined the sequence of this serine tRNA (tRNA(UCASer]. It is the longest tRNA (95 nt) known to date with an acceptor stem of 8 base pairs and lacks some of the 'invariant' nucleotides found in other tRNAs. It is the first E. coli tRNA that contains the hypermodified nucleotide i6A, adjacent to the UGA-recognizing anticodon UCA. The implications of the unusual structure and modification of this tRNA on recognition by seryl-tRNA synthetase, by tRNA modifying enzymes, and on codon recognition are discussed.
Schön
A
A
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511.
Böck
A
A
Ott
G
G
Sprinzl
M
M
Söll
D
D
D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D003062:Codon; D003545:Cysteine; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012345:RNA, Transfer, Amino Acid-Specific; D012362:RNA, Transfer, Ser / Q000235:genetics / Q000648:ultrastructure*; D012643:Selenium; D017279:Selenocysteine; D013329:Structure-Activity Relationship; D013489:Suppression, Genetic
D003062:Codon; D012345:RNA, Transfer, Amino Acid-Specific; D012362:RNA, Transfer, Ser; D017279:Selenocysteine; D000604:Amino Acyl-tRNA Synthetases; D012643:Selenium; D003545:Cysteine