Figure 1.

(A) Predicted K-turns motifs formed at the C/D and C′/D′ boxes of the pre-tRNA^Trp intron in H.volcanii and P.abyssi (left and right, respectively). The consensus K-turn structural motif derived for C/D RNAs in Eukarya and Archaea (boxed, middle part) harbors a canonical stem I, a non-canonical stem II extending from tandem sheared GA pairs, and an internal asymmetric loop of three nucleotides (20,25). (B) Structure of the two large intronic deletion mutants, Hv Del1 and Hv Del2, and of the exonic deletion Hv ExDel. The intact H.volcanii pre-tRNA^Trp structure is schematized (top line) with indication of sequence coordinates and of major sequence features (5′AE and 3′AE: 5′ and 3′ antisense elements, in blue and red, respectively).