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. 2008 Aug 20;105(34):12194–12199. doi: 10.1073/pnas.0803154105

Fig. 2.

Fig. 2.

The ultrahigh affinity of the C. perfringens X82–Dockerin interaction. (A) ELISA-based binding specificities. X82 modules from family 3 (CpGH3), 20 (CpGH20), 31 (CpGH31), and 84 (CpGH84C) glycoside hydrolases and the “large” sialidase (NanJ) fused to a CBM were probed with Doc modules from the μ-toxin, and family 2 (CpGH2), 31 (CpGH31), and 95 (CpGH95) glycoside hydrolases, which were fused to a G. stearothermophilus xylanase T6. (+) and (−) indicate detectable and no detectable binding, respectively. (B) Isothermal titration calorimetric analysis of the CpGH84CX82-μ-toxin FIVAR-Doc interaction at 30°C. (Upper) Raw heat measurements. (Lower) Integrated heats after correction for heats of dilution as determined from the heats of ligand additions at the excess of saturation. The curves represent the best fit to a single-site model. (C) Temperature dependence of ΔH for the CpGH84CX82-μ-toxin FIVAR-Doc interaction. ΔH values were determined at 30°C, 35°C, and 37°C. (D) Differential scanning calorimetric denaturation profiles of 171 μM CpGH84CX82 (X82), 198 μM μ-toxin FIVAR-Doc (FivarDoc), and 18.2 μM CpGH84C-FIVAR-Doc complex. All samples contained 5 mM CaCl2.