INTERACTIONS OF ANNEXIN-V WITH PHOSPHOLIPID MONOLAYERS

To understand the mechanism of annexin V-membrane interactions, we mea sured the interaction of human recombinant annexin V with phospholipid monolayers with differing head group and acyl group structures. Annex in V interacted with anionic phospholipid monolayers via non-specific electrostatic interactions, which was highly dependent on the surface pressure of monolayer with a sharp maximum. The unique surface pressur e dependence of the annexin V-monolayer binding is strikingly similar to that observed for the binding of Ca2+ to anionic phospholipid monol ayers, which indicates that the annexin V-bound Ca2+ binds two phospho lipids at the membrane surface and that factors governing the Ca2+-pho spholipid complex formation regulate the overall annexin V-Ca2+-membra ne interactions.