Table 2.

Classification of cyanobacterial tRNAs based on the number of nucleotides in the D-arm and variable loop regions. Based on nucleotide variation in the D-arm, the tRNAs that contained two to four nucleotides in the D-arm were classified as class I, whereas those contained four nucleotides in the D-arm were classified as class II tRNAs. Similarly, based on the nucleotide variation in the variable region, the tRNAs that contained zero to seven nucleotides were classified as class I, whereas those that contained eight to twenty-three nucleotides were classified as class II tRNAs.

tRNA class	No. of nucleotides in D-arm	tRNA
Class I	2–4	Ala, Arg, Asn, Cys, Glu, Gln, Gly, His, Leu, Lys, Met, Phe, Pro, Ser, Tyr
Class II	4	Asp, Ile, Thr, Trp, Val
No. of nucleotides in the variable region
Class I	0–7	Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, His, Ile, Lys, Phe, Pro, Thr, Trp, Val
Class II	8–23	Leu, Met, Ser, Tyr