(C-E) Liposome sedimentation assays of wild-type GRAM1b proteins (WT) and mutant versions of GRAM1b proteins carrying indicated mutations (K161A, R191A, and K161A/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 phosphatidylserine (PS) sensitivity, co-incidence detection, and anionic lipid selectivity assays; n = 12 independent experiments for WT, n = 3 independent experiments for K161A and R191A, and n = 6 independent experiments for K161A/R191A in the 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; PA, phosphatidic acid (1,2-dioleoyl-sn-glycero-3-phosphate); PI(4) P, phosphatidylinositol 4-phosphate; PI(4,5) P2, phosphatidylinositol 4,5-bisphosphate; PI, L-α-phosphatidylinositol. 