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. Author manuscript; available in PMC: 2009 Oct 6.
Published in final edited form as: Biochemistry. 2008 Jun 3;47(26):6883–6894. doi: 10.1021/bi800519a

FIGURE 4.

FIGURE 4

MA rescue of S3′S cleavage for wild-type and modified ribozymes. Cd2+ rescue reactions were carried out as indicated in the text and in Materials and Methods. (A) The metal ion-substrate contact being probed is indicated by solid dots in the model for the Tetrahymena ribozyme transition state. X represents an oxygen or sulfur atom in the oligonucleotide substrates S3′O and S3′S, respectively. (B) Rescue profiles for the wt (○), C208SP (red △), A304SP (blue △), A306SP (gray △), and U307SP (orange △) ribozymes. (C) Rescue profiles for the wt (○), C208RP (red ▽), A304RP (blue ▽), A306RP (gray ▽), and U307RP (orange ▽) ribozymes. The rescue profile of the A304SP ribozyme (blue △) is repeated from panel B to aid comparison. krel represents the observed rate constant for cleavage of S3′S relative to S3′O and was normalized to equal 1 in the absence Cd2+.