title: Two distinct sites of interaction form the calponin: gelsolin complex and two calcium switches control its activity.
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.
authors.affiliation: DIMNP, University of Montpellier 2 and 1, CNRS Montpellier, Place E, Bataillon, CC107, 34095 Montpellier Cedex 5, France.
authors.forename: Imen
authors.initials: I
authors.lastname: Ferjani
authors.forename: Abdellatif
authors.initials: A
authors.lastname: Fattoum
authors.forename: Sutherland K
authors.initials: SK
authors.lastname: Maciver
authors.forename: Mohamed
authors.initials: M
authors.lastname: Manai
authors.forename: Yves
authors.initials: Y
authors.lastname: Benyamin
authors.forename: Claude
authors.initials: C
authors.lastname: Roustan
mesh_terms: D000199:Actins / Q000737:chemistry; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry*; D002135:Calcium-Binding Proteins / Q000737:chemistry*; D002450:Cell Communication; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D018260:Gelsolin / Q000737:chemistry*; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence / Q000379:methods; D000096985:Calponins
chemical_list: D000199:Actins; D002118:Calcium; D002135:Calcium-Binding Proteins; D018260:Gelsolin; D008840:Microfilament Proteins; D010455:Peptides; D000096985:Calponins