Table 1. MICU1 in vitro binding data.
| Sample | Kd (μM) |
|---|---|
| MICU197-476 + CaCl2 | 5.4±0.7 |
| meMICU197-476 + CaCl2 | 14.0±1.5 |
| MICU197-476 R455K + CaCl2 | 6.8±0.7 |
| (me)MICU197-476 R455K + CaCl2 | 6.0±0.9 |
| MICU197-476 + IML2UCP2 | no binding |
| meMICU197-476 + IML2UCP2 | 24.6±17.7 |
| MICU197-476/IML2UCP2 + CaCl2 | 14.7±6.4 |
| meMICU197-476/IML2UCP2 + CaCl2 | 17.1±9.9 |
Dissociation constants (Kd) as determined by isothermal titration calorimetry. The errors shown correspond to the s.d. of curve fits obtained by the MicroCal Origin software version 7.0 (see Supplementary Fig. 5 for the ITC curves). The Kd provide a measure of binding affinities of MICU1 for CaCl2 and IML2UCP2. A low Kd is characteristic for high affinity/strong binding, a high Kd for low affinity/weak binding. Kd were obtained by titrating either CaCl2 or IML2UCP2 solutions into a MICU197-476 or MICU197-476/IML2UCP2 protein solution. Arginine methylation increases the Kd of MICU1 for CaCl2 that is equivalent with weaker affinity. Binding of IML2UCP2 to MICU1 restores the CaCl2 binding affinity of arginine methylated MICU1. All ITC experiments in the absence of IML2UCP2 were carried out in triplicates.