a, Gel filtration profiles of the EMC alone, the TOM complex alone, and the mixture of the EMC–TOM complexes. No peak corresponding to the assembly of the EMC–TOM complex was observed. The experiment was repeated three times yielding similar results. b, Peak fractions of the EMC–TOM mixture in a were checked by the Coomassie blue-stained SDS–PAGE gel. The band densities suggest that the peak is simply an overlap of the unbound and separate EMC and TOM. For gel source data, see Supplementary Fig. 1.