Table 1.

Comparison of C1′–C1′ distances for the base pairs of the NC helix in Kt-23 of T. thermophilus (T. th) and E. coli (E. co), Kt-7 and the U4 snRNA k-turn

	Kt-23 (T. th)		Kt-23 (E. co)		Kt-7		U4
1b•1n	G•A	9.3 Å	G•A	9.3 Å	G•A	9.2 Å	G•A	9.6 Å
2b•2n	A•U	9.9 Å	A•U	9.6 Å	A•G	9.4 Å	A•G	9.0 Å
3b•3n	U•G	11.0 Å	G•G	11.4 Å	A•G	10.0 Å	G–C	10.8 Å
4b•4n	A•A	12.3 Å	A–U	10.8 Å	G-C	10.4 Å	G–C	10.9 Å

These were measured from the PDB coordinate files 1J5E (Kt-23, T. th) (22), 2AVY (Kt-23, E. co) (23), 1FFK (Kt-7) (30) and 1E7K (U4) (6).