Biochemical Characterization of P4-ATPases

P4-ATPases have unexpected and important functions in vesicular traffic: their activities are required to support vesicle formation in the secretory and endocytic pathways. They are considered as lipid flippases, i.e. to transport lipids from the exofacial to the cytofacial monolayer of cellular membranes, in this way creating local changes in membrane curvature (Figure 1). However, direct biochemical proof for their function and key features of their activity remain to be elucidated. To provide insight into the precise role of these proteins in lipid flipping and vesicle formation, we are employing a number of biochemical and biophysical approaches to watch these pumps at work.

 

Figure 1. P4-ATPases interact with peripheral guanine-nucleotide-exchange factors (GEFs) and serve a critical role in clathrin-dependent formation of transport vesicles at the trans-Golgi network, endosomal compartment and plasma membrane. By moving lipid mass towards the cytoplasmic leaflet, ATP-driven lipid translocation might help to deform membranes. Proteins of the Cdc50 family represent a subunit for P4-ATPases regulating their localization and activity.