Updated project metadata. RAF-family kinases are activated by recruitment to the plasma membrane by GTP-bound RAS, where they initiate signaling through the MAP kinase cascade. Here we crosslinked (BS3), digested (trypsin), and analyzed via LC-MS/MS KRAS (human, residues 1-169) bound to intact BRAF (human) in an autoinhibited state with MEK1 (human, ) and a 14-3-3 (SF9) dimer . Analysis of this KRAS/BRAF/MEK1/14-3-3 complex reveals both interprotein and intraprotein crosslinks.