title: How profilin promotes actin filament assembly in the presence of thymosin beta 4.
abstract: The role of profilin in the regulation of actin assembly has been reexamined. The affinity of profilin for ATP-actin appears 10-fold higher than previously thought. In the presence of ATP, the participation of the profilin-actin complex to filament elongation at the barbed end is linked to a decrease in the steady-state concentration of globular actin. This surprising effect is made possible by the involvement of the irreversible ATP hydrolysis accompanying actin polymerization. As a consequence, in the presence of thymosin beta 4 (T beta 4), low amounts of profilin promote extensive actin assembly off of the pool of actin-T beta 4 complex. When barbed ends are capped, profilin simply sequesters globular actin. A model is proposed for the function of profilin in actin-based motility.
authors.affiliation: Laboratoire d'Enzymologie Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
authors.forename: D
authors.initials: D
authors.lastname: Pantaloni
authors.forename: M F
authors.initials: MF
authors.lastname: Carlier
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure*; D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003285:Contractile Proteins; D018260:Gelsolin / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008840:Microfilament Proteins / Q000378:metabolism / Q000502:physiology*; D051304:Profilins; D012756:Sheep; D013947:Thymosin / Q000494:pharmacology; D000099201:Thymosin beta(4)
chemical_list: D000199:Actins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003285:Contractile Proteins; D018260:Gelsolin; D008840:Microfilament Proteins; D051304:Profilins; D013947:Thymosin; D000099201:Thymosin beta(4); C495738:PFN1 protein, human