Schematic diagram of Mpl-FLAG, ▵CRM-1, and CRM-2/CRM-2 mutants. Mpl-FLAG represents FLAG-tagged wild-type Mpl, ▵CRM-1, a mutant in which the membrane-distal CRM-1 has been deleted, and CRM-2/CRM-2, a mutant in which the membrane-proximal CRM-2 of Mpl has been substituted for CRM-1.