title: FASCIN and alpha-actinin can regulate the conformation of actin filaments.
abstract: BACKGROUND
  Actin filament bundling proteins mediate numerous processes in cells such as the formation of cell membrane protrusions or cell adhesions and stress fiber based locomotion. Among them alpha-actinin and fascin are the most abundant ones. This work characterizes differences in molecular motions in actin filaments due to the binding of these two actin bundling proteins.
  
  
  METHODS
  We investigated how alpha-actinin and fascin binding modify the conformation of actin filaments by using conventional and saturation transfer EPR methods.
  
  
  RESULTS
  The result characteristic for motions on the microsecond time scale showed that both actin bundling proteins made the bending and torsional twisting of the actin filaments slower. When nanosecond time scale molecular motions were described the two proteins were found to induce opposite changes in the actin filaments. The binding of one molecule of alpha-actinin or fascin modified the conformation of numerous actin protomers.
  
  
  CONCLUSIONS
  As fascin and alpha-actinin participates in different cellular processes their binding can serve the proper tuning of the structure of actin by establishing the right conformation for the interactions with other actin binding proteins. Our observations are in correlation with the model where actin filaments fulfill their biological functions under the regulation by actin-binding proteins.
  
  
  CONCLUSIONS
  Supporting the general model for the cellular regulation of the actin cytoskeleton we showed that two abundant actin bundling proteins, fascin and alpha-actinin, alter the conformation of actin filaments through long range allosteric interactions in two different ways providing the structural framework for the adaptation to specific biological functions.
authors.affiliation: Department of Biophysics, Medical School, University of Pécs, Szigeti u. 12, Pécs H-7624, Hungary; János Szentágothai Research Center, Pécs H-7624, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Türmer
authors.affiliation: Department of Biophysics, Medical School, University of Pécs, Szigeti u. 12, Pécs H-7624, Hungary; János Szentágothai Research Center, Pécs H-7624, Hungary; MTA-PTE High Intensity Terahertz Research Group, Hungary.
authors.forename: József
authors.initials: J
authors.lastname: Orbán
authors.affiliation: Department of Biophysics and Radiation Biology, Semmelweis University of Medicine, IX. Tűzoltó u. 37-47, Budapest H-1095, Hungary.
authors.forename: Pál
authors.initials: P
authors.lastname: Gróf
authors.affiliation: Department of Biophysics, Medical School, University of Pécs, Szigeti u. 12, Pécs H-7624, Hungary; János Szentágothai Research Center, Pécs H-7624, Hungary; MTA-PTE Nuclear-Mitochondrial Interactions Research Group, Hungary. Electronic address: miklos.nyitrai@aok.pte.hu.
authors.forename: Miklós
authors.initials: M
authors.lastname: Nyitrai
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry*; D000185:Actinin / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D008840:Microfilament Proteins / Q000378:metabolism*; D008968:Molecular Conformation
chemical_list: D002352:Carrier Proteins; D008840:Microfilament Proteins; D000185:Actinin; C020324:fascin
keywords: Actin; Alpha-actinin; Bundle; EPR spectroscopy; Fascin