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. Author manuscript; available in PMC: 2018 Jun 27.
Published in final edited form as: Biochemistry. 2017 Jun 15;56(25):3283–3295. doi: 10.1021/acs.biochem.7b00188

Figure 4.

Figure 4

Cd2+ populates two types of sites on C2A with drastically different affinities. (A) Expansions of 15N-1H HSQC C2A spectra for the Cd2+ concentration range of 0–40 mM. C2A residues of the loop region respond to either one (e.g., G175, Y180, K200) or both (e.g., L142, D178, R199) binding events. Peak displacement due to the first and second binding events is shown as a blue-red gradient and monochromatic gray, respectively. (B) Representative NMR-detected binding curves constructed for the high-affinity Cd2+ sites(s). Solid lines represent the global fit of 14 residues for the high-affinity site with a Kd of 50±2µM. (C) Chemical shift perturbation plot for the low- and high-concentration regimes of Cd2+.