Nucleotide sequence of a spinach chloroplast isoleucine tRNA.

The nucleotide sequence of a spinach chloroplast isoleucine tRNA (spinach chloroplast tRNAIle1) has been determined. This tRNA has an unusual structural feature in that it contains an extra non-base paired nucleotide within the double-stranded anticodon stem. Spinach chloroplast tRNAIle1 shows surprisingly little homology to other isoleucine tRNAs. Moreover, the homology it does show is essentially equal for the isoleucine tRNAs from prokaryotes, eukaryotes, and chloroplasts. In addition, this tRNA is as homologous to the methionine elongator tRNAs of Escherichia coli and spinach chloroplasts as it is to other isoleucine tRNAs. Spinach chloroplast tRNA1Ile contains the modified residue N2,N2-dimethylguanosine which is characteristically found in eukaryotic but not in prokaryotic tRNAs.