Binding of RAP to LDLR fragments. In SPR, the LDLR fragments were immobilized on a sensor at ∼2000 resonance units (RU) for the LDLR exodomain (A) and LDLR cluster (B) and at ∼1000 resonance units for CR doublets (C–H) and tested for binding with RAP (0, 2.5, 5, 10, and 20 nm). The RAP association was recorded for 3 min followed by measuring its dissociation in the running buffer. RU, resonance units.