title: Structural characterization suggests models for monomeric and dimeric forms of full-length ezrin.
abstract: Ezrin is a member of the ERM (ezrin-radixin-moesin) family of proteins that have been conserved through metazoan evolution. These proteins have dormant and active forms, where the latter links the actin cytoskeleton to membranes. ERM proteins have three domains: an N-terminal FERM [band Four-point-one (4.1) ERM] domain comprising three subdomains (F1, F2, and F3); a helical domain; and a C-terminal actin-binding domain. In the dormant form, FERM and C-terminal domains form a stable complex. We have determined crystal structures of the active FERM domain and the dormant FERM:C-terminal domain complex of human ezrin. We observe a bistable array of phenylalanine residues in the core of subdomain F3 that is mobile in the active form and locked in the dormant form. As subdomain F3 is pivotal in binding membrane proteins and phospholipids, these transitions may facilitate activation and signaling. Full-length ezrin forms stable monomers and dimers. We used small-angle X-ray scattering to determine the solution structures of these species. As expected, the monomer shows a globular domain with a protruding helical coiled coil. The dimer shows an elongated dumbbell structure that is twice as long as the monomer. By aligning ERM sequences spanning metazoan evolution, we show that the central helical region is conserved, preserving the heptad repeat. Using this, we have built a dimer model where each monomer forms half of an elongated antiparallel coiled coil with domain-swapped FERM:C-terminal domain complexes at each end. The model suggests that ERM dimers may bind to actin in a parallel fashion.
authors.affiliation: School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Juanita M
authors.initials: JM
authors.lastname: Phang
authors.affiliation: School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Harrop
authors.affiliation: Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Duff
authors.affiliation: Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia.
authors.forename: Anna V
authors.initials: AV
authors.lastname: Sokolova
authors.affiliation: Mass Spectrometry Core Facility, University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Ben
authors.initials: B
authors.lastname: Crossett
authors.affiliation: School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: James C
authors.initials: JC
authors.lastname: Walsh
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC 3800, Australia.
authors.forename: Simone A
authors.initials: SA
authors.lastname: Beckham
authors.affiliation: School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Cuong D
authors.initials: CD
authors.lastname: Nguyen
authors.affiliation: School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Roberta B
authors.initials: RB
authors.lastname: Davies
authors.affiliation: School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Carina
authors.initials: C
authors.lastname: Glöckner
authors.affiliation: Department of Physics, University of Durham, Durham, U.K.
authors.forename: Elizabeth H C
authors.initials: EH
authors.lastname: Bromley
authors.affiliation: School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Krystyna E
authors.initials: KE
authors.lastname: Wilk
authors.affiliation: School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia Centre for Applied Medical Research, St Vincent's Hospital, Sydney, NSW 2010, Australia.
authors.forename: Paul M G
authors.initials: PM
authors.lastname: Curmi
mesh_terms: D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D003598:Cytoskeletal Proteins / Q000737:chemistry*; D019281:Dimerization; D011487:Protein Conformation; D000099149:Ezrin
chemical_list: D003598:Cytoskeletal Proteins; D000099149:Ezrin
keywords: FERM domain; crystallography; ezrin; protein dynamics; protein structure; small-angle scattering