Figure 5.

Schematics of 5′ exon mimics base pairing with the IGS of the P.carinii ribozyme. (a) The native 5′ exon, (b) the 5′ exon with a single G to C mutation at exon position –4 and (c) the 5′ exon with a G to C mutation at exon position –4 and a T to G mutation at exon position –5. The K_d values given are for the respective 5′ exon mimics binding to the IGS through base pairing and tertiary interactions (in 15 mM MgCl₂). Exon positions –2 through to –6 are deoxyribonucleotides. Note that the double mutant (c) rescues binding lost with the single mutant (b).