Supplementary Figure 1: Purification of the intact supercomplex (SC).

a. The SC was purified via a 3×FLAG tag on QcrB. b. Purification profile on 4-16% gradient SDS PAGE. Protein bands were identified by mass spectrometry as indicated. The bands marked by an asterisk (*) showed lower MS scores. Markers (kDa) are indicated. c. SC purified via the 3×FLAG-tag was subjected to SEC. The sample is highly homogenous as evident by the single peak. The elution volumes for the SEC standards Thyroglobulin (669 kDa), Apoferritin (443 kDa) and Amylase (200 kDa) were used to estimate the size of the SC (~970 kDa), as shown in the inset. d. 4-16 % gradient SDS-PAGE after SEC. e. SEC peak fractions were pooled and analyzed with BN-PAGE. Native markers are indicated. f. In order to obtain highly pure sample for mass spectrometry the BN-PAGE band was cut out and run on an SDS-PAGE. Novel components identified by MS are indicated on the left. The bands marked with an asterisk (*) showed lower scores. g. Pyridine hemochrome assay of the supercomplex, reduced minus oxidized spectrum is shown. The peaks of the corresponding hemes are indicated in the figure. The estimated ratio of heme a, b and c is 1.1:0.9:1.3.