title: Hybrid Structural Analysis of the Arp2/3 Regulator Arpin Identifies Its Acidic Tail as a Primary Binding Epitope.
abstract: Arpin is a newly discovered regulator of actin polymerization at the cell leading edge, which steers cell migration by exerting a negative control on the Arp2/3 complex. Arpin proteins have an acidic tail homologous to the acidic motif of the VCA domain of nucleation-promoting factors (NPFs). This tail is predicted to compete with the VCA of NPFs for binding to the Arp2/3 complex, thereby mitigating activation and/or tethering of the complex to sites of actin branching. Here, we investigated the structure of full-length Arpin using synchrotron small-angle X-ray scattering, and of its acidic tail in complex with an ankyrin repeats domain using X-ray crystallography. The data were combined in a hybrid model in which the acidic tail extends from the globular core as a linear peptide and forms a primary epitope that is readily accessible in unbound Arpin and suffices to tether Arpin to interacting proteins with high affinity.
authors.affiliation: Laboratoire de Pharmacologie et Biologie Appliquée, UMR 8113, CNRS-Ecole Normale Supérieure de Cachan, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France; Laboratoire d'Enzymologie et Biochimie Structurales, CNRS UPR3082, 91190 Gif-sur-Yvette, France.
authors.forename: Susan
authors.initials: S
authors.lastname: Fetics
authors.affiliation: Synchrotron SOLEIL, 91190 Gif-sur-Yvette, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Thureau
authors.affiliation: Laboratoire d'Enzymologie et Biochimie Structurales, CNRS UPR3082, 91190 Gif-sur-Yvette, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Campanacci
authors.affiliation: Institut de Biochimie et Biophysique Moléculaire et Cellulaire, CNRS-Université Paris-Sud UMR 8619, 91400 Orsay, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Aumont-Nicaise
authors.affiliation: Laboratoire d'Enzymologie et Biochimie Structurales, CNRS UPR3082, 91190 Gif-sur-Yvette, France; Ecole Polytechnique-CNRS UMR7654, 91120 Palaiseau, France.
authors.forename: Irène
authors.initials: I
authors.lastname: Dang
authors.affiliation: Laboratoire d'Enzymologie et Biochimie Structurales, CNRS UPR3082, 91190 Gif-sur-Yvette, France; Ecole Polytechnique-CNRS UMR7654, 91120 Palaiseau, France.
authors.forename: Alexis
authors.initials: A
authors.lastname: Gautreau
authors.affiliation: Synchrotron SOLEIL, 91190 Gif-sur-Yvette, France.
authors.forename: Javier
authors.initials: J
authors.lastname: Pérez
authors.affiliation: Laboratoire de Pharmacologie et Biologie Appliquée, UMR 8113, CNRS-Ecole Normale Supérieure de Cachan, 61 Avenue du Président Wilson, 94235 Cachan Cedex, France; Laboratoire d'Enzymologie et Biochimie Structurales, CNRS UPR3082, 91190 Gif-sur-Yvette, France. Electronic address: jacqueline.cherfils@ens-cachan.fr.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Cherfils
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D000939:Epitopes / Q000378:metabolism; D029941:Fish Proteins / Q000737:chemistry* / Q000378:metabolism; D005399:Fishes / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D002352:Carrier Proteins; D000939:Epitopes; D029941:Fish Proteins; C000604273:arpin protein, human