The P56S ALS-causing mutation of VAPB does not affect its interaction with FAF1 in vitro . The indicated variants of recombinant VAPB and Flag-FAF1 were incubated in vitro either alone or in combination, and then immunoprecipitated using anti-Flag beads. (A) Flag-FAF1 interacts directly with VAPB. Top panel: Schematic representation of the truncated version of VAPB (residues 1 to 210), lacking the C-terminal transmembrane region, and Flag-FAF1 full-length proteins expressed in bacteria. Bottom panel: Immunoblots of the indicated proteins in input extracts and anti-Flag immunoprecipitates. (B) The wild-type and the P56S mutant of VAPB (1 to 210), but not the K87D M89D double mutant, interact with Flag-FAF1 (right panel). IP, immunoprecipitate; WT, wild type.