title: A calcium-dependent interaction between calmodulin and the calponin homology domain of human IQGAP1.
abstract: IQGAPs are cytoskeletal scaffolding proteins which collect information from a variety of signalling pathways and pass it on to the microfilaments and microtubules. There is a well-characterised interaction between IQGAP and calmodulin through a series of IQ-motifs towards the middle of the primary sequence. However, it has been shown previously that the calponin homology domain (CHD), located at the N-terminus of the protein, can also interact weakly with calmodulin. Using a recombinant fragment of human IQGAP1 which encompasses the CHD, we have demonstrated that the CHD undergoes a calcium ion-dependent interaction with calmodulin. The CHD can also displace the hydrophobic fluorescent probe 1-anilinonaphthalene-8-sulphonate from calcium-calmodulin, suggesting that the interaction involves non-polar residues on the surface of calmodulin. Molecular modelling identified a possible site on the CHD for calmodulin interaction. The physiological significance of this interaction remains to be discovered.
authors.affiliation: School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: William J
authors.initials: WJ
authors.lastname: Andrews
authors.forename: Conor A
authors.initials: CA
authors.lastname: Bradley
authors.forename: Elaine
authors.initials: E
authors.lastname: Hamilton
authors.forename: Clare
authors.initials: C
authors.lastname: Daly
authors.forename: Thérèse
authors.initials: T
authors.lastname: Mallon
authors.forename: David J
authors.initials: DJ
authors.lastname: Timson
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000737:chemistry; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020703:ras GTPase-Activating Proteins / Q000737:chemistry* / Q000378:metabolism; D000096985:Calponins
chemical_list: D000817:Anilino Naphthalenesulfonates; D002118:Calcium; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D008840:Microfilament Proteins; D011994:Recombinant Proteins; D020703:ras GTPase-Activating Proteins; D000096985:Calponins; C101203:IQ motif containing GTPase activating protein 1; C027132:1-anilino-8-naphthalenesulfonate