Chapter 20 Notes: Phenotypic Evolution: Figure WN20.3 - De novo evolution of the hammerhead ribozyme.

Figure WN20.3 - De novo evolution of the hammerhead ribozyme.

Figure WN20.3. De novo evolution of the hammerhead ribozyme. (A) The secondary structure consists of three double helices. The arrow shows the site at which the hammerhead catalyzes its own cleavage. The core sequence at the catalytic site is shown in magenta; yellow and blue show stem regions that base-pair. X is A, U, or C. (B) The three-dimensional structure, with the cleavage site in gold. (C) Alignment of sequences present after 12 generations. Colors show similarity to the different regions of the natural hammerhead ribozyme; red shows one clone with a variant of the natural stem structure. The blue, yellow, and red sequences are diverse, but do show the base pairing required to maintain the hammerhead secondary structure (A,B). The catalytic activity is shown and is comparable with the natural ribozyme (~0.8 per minute). (These are DNA sequences: T corresponds to U in the RNA sequence.) (A,C, Redrawn from Fig. 3a,b in Salehi-Ashtiani and Szostak 2001. B, Redrawn from Fig. 1b in Doudna and Cech 2002.)

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