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Title: Structural and functional studies on ANTH and EUTH domain-containing proteins
Author: Ford, M. G. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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In this work, the crystal structure of the NH2-terminal domain of CALM, the ubiquitous isoform of AP180, is presented, both alone and bound to various inositol polyphosphates and phosphatidylinositol-4, 5-bisphosphate (PtdIns(4,5)P2). The domain has a novel, all-helical fold which we name the AP180like NH2-terminal homology (ANTH) domain. The ligands bind to the surface of the structure, to a lysine-rich motif. This lysine-rich motif was confirmed as the binding site by biochemical means and binding to PtdIns(4,5)P2 is responsible for recruiting full-length AP180 to membranes. The COOH-terminal domain of AP180 is known to bind clathrin and to stimulate clathrin lattice assembly. By simultaneously binding membranes containing PtdIns(4,5)P2 and clathrin, it is shown that AP180 can recruit clathrin to membranes. Using a novel assay where a lipid monolayer is used as a membrane mimetic, it is shown that AP180 can stimulate the polymerisation of the recruited clathrin. The resulting clathrin lattices are predominantly flat and are homogeneous in size. In the additional presence of AP2, invaginated lattices are formed. Database screens for proteins containing the lysine-rich motif identified Huntingtin Interacting Protein 1 Related (HIP1R). The NH2-terminal domain of HIPIR shares some (~20%) sequence identity with the AP180 ANTH domain. Indeed, the crystal structure of the NH2-terminal domain of HIPIR has a fold which is very similar to that of the CALM ANTH domain, showing that it, too, is an ANTH domain. HIPIR ANTH interacts with PtdIns(4,5)P2-containing membranes via its lysine rich motif. Together these observations suggest that ANTH domains may be responsible for recruiting host proteins to membranes containing PtdIns(4,5)P2. The epsin NH2-terminal homology (ENTH) domain of epsin is structurally similar to the ANTH domain - the first 7 helices superpose well - though it lacks the lysine-rich motif. However, the ENTH domain also binds to inositol polyphosphates and to membranes containing PtdIns(4,5)P2.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available