More CcmE-heme-cytochrome c-b562 complex accumulates in cells where ccmFGH are not expressed. SDS-PAGE of cell membranes stained for proteins containing covalently bound heme. The lane order is: M, molecular mass markers (as indicated, in kDa); lanes 1, cells expressing the whole Ccm system (from pEC86) and cytochrome c-b562 R98C; 2, cells expressing the whole Ccm system and cytochrome c-b562 R98C/Y101C; 3, cells expressing ccmABCDE and cytochrome c-b562 R98C; 4, cells expressing ccmABCDE and cytochrome c-b562 R98C/Y101C. An equal amount of total protein was loaded in each lane.