Anionic phosphoglycerides exert differing effects on sphingolipid transfer by ACD11, CPTP, or GLTP. In each panel, traces represent AV-SL emission intensity measured at 415 nm as a function of time resulting from the loss of AV-SL/Per-PC FRET as AV-SL is transferred to POPC vesicles. Shown are POPA effects (0–15 mol %) (a–c) and POPG effects (0–15 mol %) (d–f) on ACD11, CPTP, and GLTP (2 μg), respectively. Per-PC (nontransferable) along with AV-C1P or AV-GalCer is present at 1 mol % in the SL source vesicles at time 0. g–i, POPS effects (0–15 mol %) on ACD11, CPTP, and GLTP (2 μg), respectively. Per-PC along with AV-C1P or AV-GalCer is present at 1 mol % in the SL source vesicles at time 0. j and k summarize the C1P transfer rate changes of ACD11 and CPTP induced by POPS, POPA, and POPG. The C1P transfer rates are expressed as pmol/min transferred from SL source to POPC vesicles as a function of different amounts of anionic phosphoglycerides (0–15 mol %) present in the SL source vesicles for ACD11 (a) and CPTP (b). Red, POPA; green, POPG; blue, POPS; gray, control. Error bars, S.D.