Facilitated phospholipid flip-flop using synthetic steroid-derived translocases

Cholate esters with phenylurea groups at the 7α- and 12α-positions are highly effective promoters of phosphatidylcholine translocation across vesicle and cell membranes. The urea groups are essential for strong binding of the highly polar phosphate portion of the phosphocholine headgroup and apparently cannot be replaced by simple amide, alcohol, or amine moieties. NMR and UV studies show that these synthetic translocases have very weak affinity for phosphatidylethanolamine and phosphatidylserine. Copyright © 2002 American Chemical Society.