Schematic diagram of constructs.

Membrane-tethered Mpl construct encodes a fusion protein containing a myristylation motif derived from the first 14 amino acids of Src19 to target the fusion protein to the plasma membrane. The cytoplasmic mpl construct lacks a myristylation motif and is, therefore, predicted to be localized to the cytoplasm. Both constructs encode an FKBP12 domain harboring a phenylalanine-to-valine substitution at amino acid 36,15 allowing binding of the dimerizer AP20187 with a stoichiometry of 2:1. Red indicates myristylation peptide; hatched, FKBP12 domain; yellow, Mpl signaling domain; black, HA epitope tag.