title: Effect of short-range forces on the length distribution of fibrous cytoskeletal proteins.
abstract: The length distribution of cytoskeletal filaments is an important physical parameter, which can modulate physiological cell functions. In both eukaryotic and prokaryotic cells various biological cytoskeletal polymers form supramolecular structures due to short-range forces induced mainly by molecular crowding or cross linking proteins, but their in vivo length distribution remains difficult to measure. In general, based on experimental evidence and mathematical modeling of actin filaments in aqueous solutions, the steady state length distribution of fibrous proteins is believed to be exponential. We performed in vitro TIRF- and electron-microscopy to demonstrate that in the presence of short-range forces, which are an integral part of any living cell, the steady state length distributions of the eukaryotic cytoskeletal biopolymer actin, its prokaryotic homolog ParM and microtubule homolog FtsZ deviate from the classical exponential and are either double-exponential or Gaussian, as recent theoretical modeling predicts. Double exponential or Gaussian distributions opposed to exponential can change for example the visco-elastic properties of actin networks within the cell, influence cell motility by decreasing the amount of free ends at the leading edge of the cell or effect the assembly of FtsZ into the bacterial Z-ring thus modulating membrane constriction.
authors.affiliation: ERATO Actin Filament Dynamics Project, Japan Science and Technology Corporation, RIKEN Harima Institute, Spring 8, Sayo, Hyogo, Japan. dpopp@spring8.or.jp
authors.forename: David
authors.initials: D
authors.lastname: Popp
authors.forename: Nir S
authors.initials: NS
authors.lastname: Gov
authors.forename: Mitsusada
authors.initials: M
authors.lastname: Iwasa
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Maéda
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000648:ultrastructure; D000199:Actins / Q000737:chemistry*; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry*; D002645:Chickens; D003598:Cytoskeletal Proteins / Q000737:chemistry*; D004926:Escherichia coli / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008962:Models, Theoretical; D013314:Stress, Mechanical
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; D029968:Escherichia coli Proteins; C071525:FtsZ protein, Bacteria; C471255:ParM protein, E coli