title: The effect of ADF/cofilin and profilin on the dynamics of monomeric actin.
abstract: The main goal of the work was to uncover the dynamical changes in actin induced by the binding of cofilin and profilin. The change in the structure and flexibility of the small domain and its function in the thermodynamic stability of the actin monomer were examined with fluorescence spectroscopy and differential scanning calorimetry (DSC). The structure around the C-terminus of actin is slightly affected by the presence of cofilin and profilin. Temperature dependent fluorescence resonance energy transfer measurements indicated that both actin binding proteins decreased the flexibility of the protein matrix between the subdomains 1 and 2. Time resolved anisotropy decay measurements supported the idea that cofilin and profilin changed similarly the dynamics around the fluorescently labeled Cys-374 and Lys-61 residues in subdomains 1 and 2, respectively. DSC experiments indicated that the thermodynamic stability of actin increased by cofilin and decreased in the presence of profilin. Based on the information obtained it is possible to conclude that while the small domain of actin acts uniformly in the presence of cofilin and profilin the overall stability of actin changes differently in the presence of the studied actin binding proteins. The results support the idea that the small domain of actin behaves as a rigid unit during the opening and closing of the nucleotide binding pocket in the presence of profilin and cofilin as well. The structural arrangement of the nucleotide binding cleft mainly influences the global stability of actin while the dynamics of the different segments can change autonomously.
authors.affiliation: University of Pécs, Medical School, Department of Biophysics, Szigeti str. 12, Pécs H-7624, Hungary; Szentágothai Research Center, Ifjúság str. 34, Pécs H-7624, Hungary.
authors.forename: Roland
authors.initials: R
authors.lastname: Kardos
authors.forename: Elisa
authors.initials: E
authors.lastname: Nevalainen
authors.forename: Miklós
authors.initials: M
authors.lastname: Nyitrai
authors.forename: Gábor
authors.initials: G
authors.lastname: Hild
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000302:isolation & purification; D000255:Adenosine Triphosphate / Q000737:chemistry*; D000818:Animals; D002152:Calorimetry, Differential Scanning; D051338:Cofilin 1 / Q000737:chemistry* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D051379:Mice; D056004:Molecular Dynamics Simulation; D018482:Muscle, Skeletal / Q000737:chemistry; D051304:Profilins / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
chemical_list: D000199:Actins; C495811:Cfl1 protein, mouse; D051338:Cofilin 1; C495739:Pfn1 protein, mouse; D051304:Profilins; D011993:Recombinant Fusion Proteins; D000255:Adenosine Triphosphate
keywords: Actin; Calorimetry; Cofilin; Conformational dynamics; Fluorescence; Profilin