Figure 6.

The increase in site II Ca²⁺ binding affinity with temperature is greater for D145E than WT. Proteins double-labeled at their native cysteines with the fluorescent probe IAANS were titrated with Ca²⁺ in the presence of Mg²⁺ at 30 °C (a) or 45 °C (b). Panel (c) summarises the changes in Ca²⁺ affinity (pCa₅₀) from 21° to 45 °C, with a vertical dashed line to indicate pCa₅₀ values extrapolated to 37 °C. Protein concentration was 1 µM. Excitation was at 330 nm and emission was monitored at 450 nm. Symbols show mean ± s.e.m. (n = 4).