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The structure of phosphatidylinositol transfer protein alpha reveals sites for phospholipid binding and membrane
Claudia M van Tiel1, Arie Schouten, Gerry T Snoek
1Center for Biomembranes and Lipid Enzymology, Department of Lipid Biochemistry, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
Abstract:
Elucidation of the three-dimensional structure of phosphatidylinositol transfer protein alpha (PI-TPalpha) void of phospholipid revealed a site of membrane association connected to a channel for phospholipid binding. Near the top of the channel specific binding sites for the phosphorylcholine and phosphorylinositol head groups were identified. The structure of this open form suggests a mechanism by which PI-TPalpha preferentially binds PI from a membrane interface. Modeling predicts that upon association of PI-TPalpha with the membrane the inositol moiety of bound PI is accessible from the medium. Upon release from the membrane PI-TPalpha adopts a closed structure with the phospholipid bound fully encapsulated. This structure provides new insights as to how PI-TPalpha may play a role in PI metabolism.