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Updated: Jul 14, 2026

Pull-down of Calmodulin-binding Proteins
Published on: January 23, 2012
Two distinct sites of interaction form the calponin: gelsolin complex and two calcium switches control its activity
Imen Ferjani1, Abdellatif Fattoum, Sutherland K Maciver
1DIMNP, University of Montpellier 2 and 1, CNRS Montpellier, Place E, Bataillon, CC107, 34095 Montpellier Cedex 5, France.
Abstract:
Gelsolin and calponin are well characterized actin-binding proteins that form a tight gelsolin:calponin complex (GCC). We show here that the GCC is formed through two distinct interfaces. One of these is formed between 144-182 of calponin and 25-150 of gelsolin (G1). The second is a calcium-sensitive site centred on calponin's CH domain, and the C-terminal half of gelsolin (G4-6). The behaviour of this second interface is dependent on the presence of calcium and so it is possible that potential GCC-binding partners may be selected by calcium availability. Actin is one such GCC-binding partner and we show that a larger complex is formed with monomeric actin in calcium. The stoichiometry of this complex is determined to be 1 gelsolin/1 calponin/2 G-actins (GCA(2)). Both actin monomers bind the GCC through gelsolin. Both calponin and gelsolin are reported to play signaling roles in addition to their better-characterized actin-binding properties and it is possible that the GCC regulates both of these functions.
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