title: Open conformation of ezrin bound to phosphatidylinositol 4,5-bisphosphate and to F-actin revealed by neutron scattering.
abstract: Ezrin is a member of the ezrin-radixin-moesin family (ERM) of adapter proteins that are localized at the interface between the cell membrane and the cortical actin cytoskeleton, and they regulate a variety of cellular functions. The structure representing a dormant and closed conformation of an ERM protein has previously been determined by x-ray crystallography. Here, using contrast variation small angle neutron scattering, we reveal the structural changes of the full-length ezrin upon binding to the signaling lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)) and to F-actin. Ezrin binding to F-actin requires the simultaneous binding of ezrin to PIP(2). Once bound to F-actin, the opened ezrin forms more extensive contacts with F-actin than generally depicted, suggesting a possible role of ezrin in regulating the interfacial structure and dynamics between the cell membrane and the underlying actin cytoskeleton. In addition, using gel filtration, we find that the conformational opening of ezrin in response to PIP(2) binding is cooperative, but the cooperativity is disrupted by a phospho-mimic mutation S249D in the 4.1-ezrin/radixin/moesin (FERM) domain of ezrin. Using surface plasmon resonance, we show that the S249D mutation weakens the binding affinity and changes the kinetics of 4.1-ERM to PIP(2) binding. The study provides the first structural view of the activated ezrin bound to PIP(2) and to F-actin.
authors.affiliation: Department of Chemistry, City College of New York, New York, New York 10031, USA.
authors.forename: Jayant James
authors.initials: JJ
authors.lastname: Jayasundar
authors.forename: Jeong Ho
authors.initials: JH
authors.lastname: Ju
authors.forename: Lilin
authors.initials: L
authors.lastname: He
authors.forename: Dazhi
authors.initials: D
authors.lastname: Liu
authors.forename: Flora
authors.initials: F
authors.lastname: Meilleur
authors.forename: Jinkui
authors.initials: J
authors.lastname: Zhao
authors.forename: David J E
authors.initials: DJ
authors.lastname: Callaway
authors.forename: Zimei
authors.initials: Z
authors.lastname: Bu
mesh_terms: D000199:Actins / Q000737:chemistry*; D019943:Amino Acid Substitution; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D033363:Neutron Diffraction; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry*; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D053838:Scattering, Small Angle; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry; D020349:Surface Plasmon Resonance; D014961:X-Ray Diffraction; D000099149:Ezrin
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; D000099149:Ezrin; C093376:sodium-hydrogen exchanger regulatory factor