title: Asymmetric mode of Ca²⁺-S100A4 interaction with nonmuscle myosin IIA generates nanomolar affinity required for filament remodeling.
abstract: Filament assembly of nonmuscle myosin IIA (NMIIA) is selectively regulated by the small Ca²⁺-binding protein, S100A4, which causes enhanced cell migration and metastasis in certain cancers. Our NMR structure shows that an S100A4 dimer binds to a single myosin heavy chain in an asymmetrical configuration. NMIIA in the complex forms a continuous helix that stretches across the surface of S100A4 and engages the Ca²⁺-dependent binding sites of each subunit in the dimer. Synergy between these sites leads to a very tight association (K(D) ∼1 nM) that is unique in the S100 family. Single-residue mutations that remove this synergy weaken binding and ameliorate the effects of S100A4 on NMIIA filament assembly and cell spreading in A431 human epithelial carcinoma cells. We propose a model for NMIIA filament disassembly by S100A4 in which initial binding to the unstructured NMIIA tail initiates unzipping of the coiled coil and disruption of filament packing.
authors.affiliation: Institute of Integrative Biology, BioSciences Building, Crown Street, University of Liverpool, Liverpool L69 7ZB, UK.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Elliott
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Irvine
authors.forename: Hyun Suk
authors.initials: HS
authors.lastname: Jung
authors.forename: Kaeko
authors.initials: K
authors.lastname: Tozawa
authors.forename: Martyna W
authors.initials: MW
authors.lastname: Pastok
authors.forename: Remigio
authors.initials: R
authors.lastname: Picone
authors.forename: Sandip K
authors.initials: SK
authors.lastname: Badyal
authors.forename: Jaswir
authors.initials: J
authors.lastname: Basran
authors.forename: Philip S
authors.initials: PS
authors.lastname: Rudland
authors.forename: Roger
authors.initials: R
authors.lastname: Barraclough
authors.forename: Lu-Yun
authors.initials: LY
authors.lastname: Lian
authors.forename: Clive R
authors.initials: CR
authors.lastname: Bagshaw
authors.forename: Marina
authors.initials: M
authors.lastname: Kriajevska
authors.forename: Igor L
authors.initials: IL
authors.lastname: Barsukov
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement; D003599:Cytoskeleton / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D024507:Nonmuscle Myosin Type IIA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D017354:Point Mutation; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D011994:Recombinant Proteins; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; C077591:S100A4 protein, human; D024507:Nonmuscle Myosin Type IIA; D002118:Calcium