Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness

Hyeran Kang, Michael J. Bradley, Brannon R. McCullough, Anaëlle Pierre, Elena E. Grintsevich, Emil Reisler, Enrique M. De La Cruz

Research output: Contribution to journalArticle

45 Scopus citations

Abstract

The assembly of actin monomers into filaments and networks plays vital roles throughout eukaryotic biology, including intracellular transport, cell motility, cell division, determining cellular shape, and providing cells with mechanical strength. The regulation of actin assembly and modulation of filament mechanical properties are critical for proper actin function. It is well established that physiological salt concentrations promote actin assembly and alter the overall bending mechanics of assembled filaments and networks. However, the molecular origins of these salt-dependent effects, particularly if they involve nonspecific ionic strength effects or specific ion-binding interactions, are unknown. Here, we demonstrate that specific cation binding at two discrete sites situated between adjacent subunits along the long-pitch helix drive actin polymerization and determine the filament bending rigidity. We classify the two sites as "polymerization" and "stiffness" sites based on the effects that mutations at the sites have on salt-dependent filament assembly and bending mechanics, respectively. These results establish the existence and location of the cation-binding sites that confer salt dependence to the assembly and mechanics of actin filaments.

Original languageEnglish (US)
Pages (from-to)16923-16927
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number42
DOIs
StatePublished - Oct 16 2012

Keywords

  • Ion-linkage
  • Persistence length
  • Polyelectrolyte
  • Structural bioinformatics

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