Fig. 5.

(a) Movement of HSQC peaks for CaM bound with 6 MEs Ca²⁺ followed by titration of Pb²⁺ from 0–3 MEs in 0.5 ME increments. Residues in the C-terminal domain exhibit stable chemical shifts, while significant changes are observed for residues D78, D80, S81, E82, E83 and R86, which suggests a potential Pb²⁺-binding site in the linker region (74–82). (b) Residues in sites EF-I and EF-II, but not EF-III and EF-IV, disappear with addition of Pb²⁺ to Ca²⁺:CaM complex. (c) Similar results are observed for residues I27 and I63 occupying position 8 in the EF loop regions of sites EF-I and EF-II only.