Figure 4.

Structural and biochemical analysis for comparison with Ca²⁺-bound MICU1. (a) Cartoon representations of the superimposed apo heterodimer and one molecule of Ca²⁺-bound MICU1 (gray) (PDB ID 4nsd; Wang et al., 2014 ▸), and a detailed view of interface 2 of the superimposed structure. The 18° tilt of α12 helix of MICU1 EF-hand 3 is indicated by a red arrow. The heterodimer is colored violet (MICU1) and cyan (MICU2). (b) SEC profile of the MICU1–MICU2 or MICU1–MICU2^MUT heterodimer, and (c) its SDS–PAGE results in the absence (marked by Apo) or presence of Ca²⁺ (marked by Ca²⁺). The black arrows indicate the peak fractions of each SDS gel. The two black arrows in the MICU1–MICU2^MUT(Ca²⁺) heterodimer indicate the peak fractions of MICU1 and MICU2 (left and right), respectively. (d) A cartoon representation of the superimposed interface 1 of the apo MICU1–MICU2 heterodimer with one molecule of Ca²⁺-bound MICU1 (gray) (PDB ID 4nsd) based on MICU1 in the heterodimer. The conformational changes of MICU1 EF-hand 1 including the Asp231 and Leu232 residue are indicated by a stick representation and black arrows.