Figure 4.

Measurements of binding affinities of various coenzyme B₁₂ aptamers. (A) Representative plot of the ligand concentration-dependent modulation of spontaneous RNA cleavage using the 206 btuB fragment from S.typhimurium. The fraction of RNA cleaved at sites 1–5 (Fig. 3C) was normalized against the fraction cleaved at each site when incubated in the absence of coenzyme B₁₂. Site 5 is not present in the preceding image, but is present in the larger RNA construct used for this K_D analysis (data not shown). (B) Comparison of the apparent K_D values for various coenzyme B₁₂ aptamer constructs from several bacteria. Values were derived for each construct using the approach described in (A).