Fig. 1.

Isolation of aptamers for discrete functional sites on the surface of TATA-binding protein (TBP). (A) A structural model representing the DNA·TBP·TFIIA·TFIIB quaternary complex (taken from ref. 19). TBP in black, and flanking TFIIB, the two subunits of TFIIA in gray are shown as ribbon models; the DNA is represented using a space-filling model. Human TFIIB was modeled with the crystal structure of the yeast tertiary complex. (B) Predicted secondary structure of AptTBP-12 and AptTBP-101, respectively, using mfold developed by Zuker (18). Capital letters represent randomized region, and lowercase letters signify the constant regions. The “true” aptamer moiety defined by mutagenesis is enclosed in the box.