Calcium ion exchange in crystalline gelsolin

Sakesit Chumnarnsilpa, Anantasak Loonchanta, Bo Xue, Han Choe, Dunja Urosev, Hui Wang, Uno Lindberg, Leslie D. Burtnick, Robert C. Robinson

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Gelsolin is a calcium and pH-sensitive modulator of actin filament length. Here, we use X-ray crystallography to examine the extraction and exchange of calcium ions from their binding sites in different crystalline forms of the activated N and C-terminal halves of gelsolin, G1-G3 and G4-G6, respectively. We demonstrate that the combination of calcium and low pH activating conditions do not induce conformational changes in G4-G6 beyond those elicited by calcium alone. EGTA is able to remove calcium ions bound to the type I and type II metal ion-binding sites in G4-G6. Constrained by crystal contacts and stabilized by interdomain interaction surfaces, the gross structure of calcium-depleted G4-G6 remains that of the activated form. However, high-resolution details of changes in the ion-binding sites may represent the initial steps toward restoration of the arrangement of domains found in the calcium-free inactive form of gelsolin in solution. Furthermore, bathing crystals with the trivalent calcium ion mimic, Tb3+, results in anomalous scattering data that permit unequivocal localization of terbium ions in each of the proposed type I and type II ion-binding sites of both halves of gelsolin. In contrast to predictions based on solution studies, we find that no calcium ion is immune to exchange.

Original languageEnglish
Pages (from-to)773-782
Number of pages10
JournalJournal of Molecular Biology
Issue number3
Publication statusPublished - Mar 31 2006
Externally publishedYes


  • Actin
  • Calcium activation
  • Conformational change
  • Gelsolin
  • Protein crystallography

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Molecular Biology


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