Formin is a processive motor that requires profilin to accelerate actin assembly and associated ATP hydrolysis.
Motile and morphogenetic cellular processes are driven by site-directed assembly of actin filaments. Formins, proteins characterized by formin homology domains FH1 and FH2, are initiators of actin assembly. How formins simply bind to filament barbed ends in rapid equilibrium or find free energy to become a processive motor of filament assembly remains enigmatic. Here we demonstrate that the FH1-FH2 domain accelerates hydrolysis of ATP coupled to profilin-actin polymerization and uses the derived free energy for processive polymerization, increasing 15-fold the rate constant for profilin-actin association to barbed ends. Profilin is required for and takes part in the processive function. Single filaments grow at least 10 microm long from formin bound beads without detaching. Transitory formin-associated processes are generated by poisoning of the processive cycle by barbed-end capping proteins. We successfully reconstitute formin-induced motility in vitro, demonstrating that this mechanism accounts for the puzzlingly rapid formin-induced actin processes observed in vivo.
Romero
Stéphane
S
Laboratoire d'Enzymologie et Biochimie Structurales, Centre National de la Recherche Scientifique, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France.
Le Clainche
Christophe
C
Didry
Dominique
D
Egile
Coumaran
C
Pantaloni
Dominique
D
Carlier
Marie-France
MF
D000199:Actins / Q000096:biosynthesis*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D003285:Contractile Proteins / Q000378:metabolism*; D005326:Fetal Proteins / Q000378:metabolism*; D000080865:Formins; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D008863:Microspheres; D020409:Molecular Motor Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D051304:Profilins
D000199:Actins; D002352:Carrier Proteins; D003285:Contractile Proteins; C491464:Diap1 protein, mouse; D005326:Fetal Proteins; D000080865:Formins; D008840:Microfilament Proteins; D020409:Molecular Motor Proteins; D009687:Nuclear Proteins; C495739:Pfn1 protein, mouse; D051304:Profilins; D000255:Adenosine Triphosphate