HRG interacts with negatively charged lipids. (A) Analysis of HRG^PID (1 μg/mL) binding to an array of different cellular lipids using PIP Strips and SphingoStrips coated with 100 pmoles of the indicated biologically active lipids. (B) Analysis of the ability of HRG^PID to bind various phospholipids by ELISA using wells precoated with 50 μg/mL cardiolipin, sulfatide, PtdIns, and PtdIns(4)P, with ethanol coated wells being included as a negative control. (C) Ability of HRG in a HRG^P preparation (100 μg/mL) to bind to viable pgsA-745 cells precoated with cardiolipin, sulfatide, PtdIns, and PtdIns(4)P (50 μg/mL, room temperature, 30 minutes). HRG binding was detected by flow cytometry. Representative flow cytometry histograms are shown, with filled black histograms representing Ab-only control and filled gray and open black histograms representing HRG binding to untreated or phospholipid coated cells, respectively.