(D-E) Liposome sedimentation assays of wild-type GRAM1b proteins (WT) and mutant versions of GRAM1b proteins carrying indicated mutations (R189W, R189W/R191A). Liposomes containing the indicated mole% lipids were incubated with purified GRAM1b proteins as shown. Bound proteins [pellet, (P)] were separated from the unbound proteins [supernatant, (S)], run on SDS-PAGE and visualized by colloidal blue staining [mean ± SEM, n = 3 independent experiments for all conditions in the co-incidence detection assay; n = 3 independent experiments for R189W and R189W/R191A, n = 6 independent experiments for WT in phosphatidylserine (PS) sensitivity assay; n = 3 independent experiments for R189W and R189W/R191A, n = 5 independent experiments for WT in cholesterol sensitivity assay]. DOPC, phosphatidylcholine (1,2-dioleoyl-sn-glycero-3-phosphocholine); DOPS, phosphatidylserine (1,2-dioleoyl-sn-glycero-3-phospho-L-serine); Chol., cholesterol. 