Figure 3.

Photoaffinity labeling of complex I by [¹²⁵I]-43. (A) SMPs (4.0 mg of protein/mL) were labeled by [¹²⁵I]-43 (10 nM), followed by the purification of complex I by BN-PAGE and electroelution. The isolated complex I was resolved by doubled SDS-PAGE, and the SDS gel was subjected to silver staining or autoradiography. (B) The subunits labeled by [¹²⁵I]-43 in bovine complex I. The 49-kDa (pink), ND1 (orange), and PSST (blue) subunits in complex I (PDB ID: 5O31)¹⁸ are shown. The quinone-accessing cavity is formed at the interface of the 49-kDa, ND1, and PSST subunits as indicated by a black sphere generated using MOLE with a 1.4-Å probe (https://mol.upol.cz).¹⁹