Investigating a back door mechanism of actin phosphate release by steered molecular dynamics

Willy Wriggers, Klaus J Schulten

Research output: Contribution to journalArticlepeer-review

Abstract

In actin-based cell motility, phosphate P(i) release after ATP hydrolysis is an essential biochemical process, but the actual pathway of P(i) separation from actin is not well understood. We report a series of molecular dynamics simulations that induce the dissociation of P(i) from actin. After cleavage from ATP, the singly protonated phosphate (HPO42-) rotates about the ADP-associated Ca2+ ion, turning away from the negatively charged ADP towards the putative exit near His73. To reveal the microscopic processes underlying the release of P(i), adhesion forces were measured when pulling the substrate out of its binding pocket. The results suggest that the separation from the divalent cation is the rate-limiting step in P(i) release. Protonation of HPO42- to H2PO4- lowers the electrostatic barrier during P(i) liberation from the ion. The simulations revealed a propensity of charged His73+ to form a salt bridge with HPO42-, but not with H2PO4-. His73 stabilizes HPO42- and, thereby, inhibits rapid P(i) release from actin. Arg177 remains attached to P(i) along the putative back door pathway, suggesting a shuttle function that facilitates the transport of P(i) to a binding site on the protein surface.

Original languageEnglish (US)
Pages (from-to)262-273
Number of pages12
JournalProteins: Structure, Function and Genetics
Volume35
Issue number2
DOIs
StatePublished - May 1 1999

Keywords

  • Actin function
  • ATP hydrolysis
  • Divalent cation
  • Non- equilibrium molecular dynamics
  • Phosphate titration

ASJC Scopus subject areas

  • Genetics
  • Structural Biology
  • Biochemistry

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