Figure 4

Predicted secondary structures for three homologous cryptophyte tRNAs. Hemiselmis andersenii 'trnK(uuu)' (A) is paralogous to trnS(gcu) (B). Duplication and divergence of an ancestral trnS(gcu) appears to have led to the evolution of 'trnK(uuu)' in H. andersenii (A), which consequently, possesses an atypically long variable region. The anticodon loop and the variable region of 'trnK(uuu)' is AT-rich and the predicted stem regions consist entirely of A-T base pairings. Furthermore, the loop of the anticodon loop/stem region is missing one nucleotide (arrow). These structural considerations suggest that 'trnK(uuu)' may not be functional. The 'trnK(uuu)' gene in H. andersenii (A) is orthologous to trnS(gcu) in R. salina (C). Note that while sequences within the anticodon loop, V-arm, and acceptor stem are divergent between the two orthologous copies, sequences within the D loop and the T loop are conserved.