title: Control of actin dynamics by proteins made of beta-thymosin repeats: the actobindin family.
abstract: Actobindin is an actin-binding protein from amoeba, which consists of two beta-thymosin repeats and has been shown to inhibit actin polymerization by sequestering G-actin and by stabilizing actin dimers. Here we show that actobindin has the same biochemical properties as the Drosophila or Caenorhabditis elegans homologous protein that consists of three beta-thymosin repeats. These proteins define a new family of actin-binding proteins. They bind G-actin in a 1:1 complex with thermodynamic and kinetic parameters similar to beta-thymosins. Like beta-thymosins, they slow down nucleotide exchange on G-actin and make a ternary complex with G-actin and Latrunculin A. On the other hand, they behave as functional homologs of profilin because their complex with MgATP-G-actin, unlike beta-thymosin-actin, participates in filament barbed end growth, like profilin-actin complex. Therefore these proteins play an active role in actin-based motility processes. In addition, proteins of the actobindin family interact with the pointed end of actin filaments and inhibit pointed end growth, maybe via the interaction of the beta-thymosin repeats with two terminal subunits.
authors.affiliation: Dynamique du Cytosquelette, Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, 91198 Gif-sur-Yvette, France.
authors.forename: Maud
authors.initials: M
authors.lastname: Hertzog
authors.forename: Elena G
authors.initials: EG
authors.lastname: Yarmola
authors.forename: Dominique
authors.initials: D
authors.lastname: Didry
authors.forename: Michael R
authors.initials: MR
authors.lastname: Bubb
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Carlier
mesh_terms: D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D004330:Drosophila / Q000378:metabolism; D029721:Drosophila Proteins; D007700:Kinetics; D008840:Microfilament Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins; D015800:Protozoan Proteins; D013947:Thymosin / Q000378:metabolism*
chemical_list: D000199:Actins; D002352:Carrier Proteins; D029721:Drosophila Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D015800:Protozoan Proteins; C050869:actobindin protein, Acanthamoeba; C414741:cib protein, Drosophila; D013947:Thymosin; D000255:Adenosine Triphosphate