Structural evidence for the roles of divalent cations in actin polymerization and activation of ATP hydrolysis

Clement P.M. Scipion, Umesh Ghoshdastider, Fernando J. Ferrer, Tsz Ying Yuen, Jantana Wongsantichon, Robert C. Robinson

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


The structure of the actin filament is known at a resolution that has allowed the architecture of protein components to be unambiguously assigned. However, fully understanding the chemistry of the system requires higher resolution to identify the ions and water molecules involved in polymerization and ATP hydrolysis. Here, we find experimental evidence for the association of cations with the surfaces of G-Actin in a 2.0-A resolution X-ray structure of actin bound to a Cordon-Bleu WH2 motif and in previously determined high-resolution X-ray structures. Three of four reoccurring divalent cation sites were stable during molecular dynamics (MD) simulations of the filament, suggesting that these sites may play a functional role in stabilizing the filament. We modeled the water coordination at the ATP-bound Mg2+, which also proved to be stable during the MD simulations. Using this model of the filament with a hydrated ATP-bound Mg2+, we compared the cumulative probability of an activated hydrolytic water molecule approaching the γ-phosphorous of ATP, in comparison with G-Actin, in the MD simulations. The cumulative probability increased in F-Actin in line with the activation of actin's ATPase activity on polymerization. However, inclusion of the cations in the filament lowered cumulative probability, suggesting the rate of hydrolysis may be linked to filament flexibility. Together, these data extend the possible roles of Mg2+ in polymerization and the mechanism of polymerizationinduced activation of actin's ATPase activity.

Original languageEnglish
Pages (from-to)10345-10350
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number41
Publication statusPublished - Oct 9 2018

ASJC Scopus subject areas

  • General


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