2jkr
From Proteopedia
AP2 CLATHRIN ADAPTOR CORE with Dileucine peptide RM(phosphoS)QIKRLLSE
Structural highlights
FunctionAP2B1_HUMAN Component of the adaptor protein complex 2 (AP-2). Adaptor protein complexes function in protein transport via transport vesicles in different membrane traffic pathways. Adaptor protein complexes are vesicle coat components and appear to be involved in cargo selection and vesicle formation. AP-2 is involved in clathrin-dependent endocytosis in which cargo proteins are incorporated into vesicles surrounded by clathrin (clathrin-coated vesicles, CCVs) which are destined for fusion with the early endosome. The clathrin lattice serves as a mechanical scaffold but is itself unable to bind directly to membrane components. Clathrin-associated adaptor protein (AP) complexes which can bind directly to both the clathrin lattice and to the lipid and protein components of membranes are considered to be the major clathrin adaptors contributing the CCV formation. AP-2 also serves as a cargo receptor to selectively sort the membrane proteins involved in receptor-mediated endocytosis. AP-2 seems to play a role in the recycling of synaptic vesicle membranes from the presynaptic surface. AP-2 recognizes Y-X-X-[FILMV] (Y-X-X-Phi) and [ED]-X-X-X-L-[LI] endocytosis signal motifs within the cytosolic tails of transmembrane cargo molecules. AP-2 may also play a role in maintaining normal post-endocytic trafficking through the ARF6-regulated, non-clathrin pathway. The AP-2 beta subunit acts via its C-terminal appendage domain as a scaffolding platform for endocytic accessory proteins; at least some clathrin-associated sorting proteins (CLASPs) are recognized by their [DE]-X(1,2)-F-X-X-[FL]-X-X-X-R motif. The AP-2 beta subunit binds to clathrin heavy chain, promoting clathrin lattice assembly; clathrin displaces at least some CLASPs from AP2B1 which probably then can be positioned for further coat assembly.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMost transmembrane proteins are selected as transport vesicle cargo through the recognition of short, linear amino acid motifs in their cytoplasmic portions by vesicle coat proteins. In the case of clathrin-coated vesicles (CCVs) the motifs are recognised by clathrin adaptors. The AP2 adaptor complex (subunits alpha,beta2,mu2,sigma2) recognises both major endocytic motifs: YxxPhi motifs and [DE]xxxL[LI] acidic dileucine motifs. Here we describe the binding of AP2 to the endocytic dileucine motif from CD4 . The major recognition events are the two leucine residues binding in hydrophobic pockets on sigma2. The hydrophilic residue four residues upstream from the first leucine sits on a positively charged patch made from residues on sigma2 and alpha subunits. Mutations in key residues inhibit the binding of AP2 to 'acidic dileucine' motifs displayed in liposomes containing PtdIns4,5P(2), but do not affect binding to YxxPhi motifs via mu2. In the 'inactive' AP2 core structure , both motif binding sites are blocked by different parts of the beta2 subunit. To allow a dileucine motif to bind, the beta2 N-terminus is displaced and becomes disordered; however, in this structure the YxxPhi binding site on mu2 remains blocked. A structural explanation for the binding of endocytic dileucine motifs by the AP2 complex.,Kelly BT, McCoy AJ, Spate K, Miller SE, Evans PR, Honing S, Owen DJ Nature. 2008 Dec 18;456(7224):976-979. doi: 10.1038/nature07422. PMID:19140243[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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