title: A large-scale conformational change couples membrane recruitment to cargo binding in the AP2 clathrin adaptor complex.
abstract: The AP2 adaptor complex (alpha, beta2, sigma2, and mu2 subunits) crosslinks the endocytic clathrin scaffold to PtdIns4,5P(2)-containing membranes and transmembrane protein cargo. In the "locked" cytosolic form, AP2's binding sites for the two endocytic motifs, YxxPhi on the C-terminal domain of mu2 (C-mu2) and [ED]xxxL[LI] on sigma2, are blocked by parts of beta2. Using protein crystallography, we show that AP2 undergoes a large conformational change in which C-mu2 relocates to an orthogonal face of the complex, simultaneously unblocking both cargo-binding sites; the previously unstructured mu2 linker becomes helical and binds back onto the complex. This structural rearrangement results in AP2's four PtdIns4,5P(2)- and two endocytic motif-binding sites becoming coplanar, facilitating their simultaneous interaction with PtdIns4,5P(2)/cargo-containing membranes. Using a range of biophysical techniques, we show that the endocytic cargo binding of AP2 is driven by its interaction with PtdIns4,5P(2)-containing membranes.
authors.affiliation: Cambridge Institute for Medical Research, Department of Clinical Biochemistry, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK.
authors.forename: Lauren P
authors.initials: LP
authors.lastname: Jackson
authors.forename: Bernard T
authors.initials: BT
authors.lastname: Kelly
authors.forename: Airlie J
authors.initials: AJ
authors.lastname: McCoy
authors.forename: Thomas
authors.initials: T
authors.lastname: Gaffry
authors.forename: Leo C
authors.initials: LC
authors.lastname: James
authors.forename: Brett M
authors.initials: BM
authors.lastname: Collins
authors.forename: Stefan
authors.initials: S
authors.lastname: Höning
authors.forename: Philip R
authors.initials: PR
authors.lastname: Evans
authors.forename: David J
authors.initials: DJ
authors.lastname: Owen
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000737:chemistry*; D001665:Binding Sites; D002462:Cell Membrane / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D010716:Phosphatidylinositols / Q000737:chemistry; D011487:Protein Conformation
chemical_list: D033962:Adaptor Protein Complex 2; D008024:Ligands; D010716:Phosphatidylinositols