Mutations in the Tetrahymena ribozyme internal guide sequence: effects on docking of the P1 helix into the catalytic core and correlation with catalytic activity.
Campbell TB, Cech TR, Biochemistry, 1996 Sep 3 - link

Tertiary interactions with the internal guide sequence mediate docking of the P1 helix into the catalytic core of the Tetrahymena ribozyme.
Strobel SA, Cech TR, Biochemistry, 1993 Dec 14 - link