title: Analysis of tetramethylrhodamine-labeled actin polymerization and interaction with actin regulatory proteins.
abstract: The hydrolysis of ATP accompanying actin polymerization destabilizes the filament, controls actin assembly dynamics in motile processes, and allows the specific binding of regulatory proteins to ATP- or ADP-actin. However, the relationship between the structural changes linked to ATP hydrolysis and the functional properties of actin is not understood. Labeling of actin Cys374 by tetramethylrhodamine (TMR) has been reported to make actin non-polymerizable and enabled the crystal structures of ADP-actin and 5'-adenylyl beta,gamma-imidodiphosphate-actin to be solved. TMR-actin has also been used to solve the structure of actin in complex with the formin homology 2 domain of mammalian Dia1. To understand how the covalent modification of actin by TMR may affect the structural changes linked to ATP hydrolysis and to evaluate the functional relevance of crystal structures of TMR-actin in complex with actin-binding proteins, we have analyzed the assembly properties of TMR-actin and its interaction with regulatory proteins. We show that TMR-actin polymerized in very short filaments that were destabilized by ATP hydrolysis. The critical concentrations for assembly of TMR-actin in ATP and ADP were only an order of magnitude higher than those for unlabeled actin. The functional interactions of actin with capping proteins, formin, actin-depolymerizing factor/cofilin, and the VCA-Arp2/3 filament branching machinery were profoundly altered by TMR labeling. The data suggest that TMR labeling hinders the intramolecular movements of actin that allow its specific adaptative recognition by regulatory proteins and that determine its function in the ATP- or ADP-bound state.
authors.affiliation: Dynamique du Cytosquelette, Laboratoire d'Enzymologie et Biochimie Structurale, CNRS, avenue de la Terrasse, 91198 Gif-sur-Yvette, France.
authors.forename: Andrea
authors.initials: A
authors.lastname: Pelikan Conchaudron
authors.forename: Dominique
authors.initials: D
authors.lastname: Didry
authors.forename: Kim Ho Diep
authors.initials: KH
authors.lastname: Le
authors.forename: Eric
authors.initials: E
authors.lastname: Larquet
authors.forename: Nicolas
authors.initials: N
authors.lastname: Boisset
authors.forename: Dominique
authors.initials: D
authors.lastname: Pantaloni
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Carlier
mesh_terms: D051344:Actin Capping Proteins / Q000378:metabolism*; D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D051339:Actin Depolymerizing Factors / Q000378:metabolism; D051377:Actin-Related Protein 2 / Q000378:metabolism; D051378:Actin-Related Protein 3 / Q000378:metabolism; D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D051345:Destrin / Q000378:metabolism; D005326:Fetal Proteins / Q000378:metabolism; D000080865:Formins; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism* / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D012235:Rhodamines / Q000378:metabolism*
chemical_list: D051344:Actin Capping Proteins; D051339:Actin Depolymerizing Factors; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; C495824:DSTN protein, human; D051345:Destrin; D005326:Fetal Proteins; D000080865:Formins; D008840:Microfilament Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D012235:Rhodamines; D000244:Adenosine Diphosphate; C005358:tetramethylrhodamine