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. Author manuscript; available in PMC: 2019 Mar 19.
Published in final edited form as: Nature. 2018 Sep 19;562(7726):277–280. doi: 10.1038/s41586-018-0557-5

Figure 3. Structure and mechanism of Ring nucleases.

Figure 3

a, Structure of the CARF domain of Sso1393 with cA4 docked. The active site residues K168 and S11 are shown. b, Kinetic analysis of Sso1393 (wild-type, S11A and K168A variants) and Sso2081 (wild-type, S11A and R105A/K106A variants). Catalytic rate constants under single turnover conditions are plotted. The data points are derived from exponential fits to the triplicate rate measurements presented in Extended Data Fig. 8, with the standard errors derived from curve fitting shown. c, Cartoon showing the reaction scheme for conversion of cyclic to linear A4>P and A2>P. S11 may participate in the correct positioning of the 2’-OH group of the ribose to facilitate nucleophilic attack, whilst the basic residue K168 (and R105/K106 in Sso2081) may stabilise the penta-covalent phosphorus formed in the transition state.