(B) Digitonin-solubilized (1 or 4 g/g digitonin/protein ratio, as indicated) mitochondrial membranes from the indicated yeast strains (wild type, pex19Δ, pex19Δmsp1Δ) expressing Pex13-V5 (under its endogenous promotor) were separated by BN-PAGE with a 3-18% gradient and stained with Coomassie brilliant blue. BHM, bovine heart mitochondria; V2, complex V-dimer; SL,supercomplex III2IV2; Ss, supercomplex III2IV1; V1, complex V-monomer. 