title: Structure/function implications in a dynamic complex of the intrinsically disordered Sic1 with the Cdc4 subunit of an SCF ubiquitin ligase.
abstract: Intrinsically disordered proteins can form highly dynamic complexes with partner proteins. One such dynamic complex involves the intrinsically disordered Sic1 with its partner Cdc4 in regulation of yeast cell cycle progression. Phosphorylation of six N-terminal Sic1 sites leads to equilibrium engagement of each phosphorylation site with the primary binding pocket in Cdc4, the substrate recognition subunit of a ubiquitin ligase. ENSEMBLE calculations using experimental nuclear magnetic resonance and small-angle X-ray scattering data reveal significant transient structure in both phosphorylation states of the isolated ensembles (Sic1 and pSic1) that modulates their electrostatic potential, suggesting a structural basis for the proposed strong contribution of electrostatics to binding. A structural model of the dynamic pSic1-Cdc4 complex demonstrates the spatial arrangements in the ubiquitin ligase complex. These results provide a physical picture of a protein that is predominantly disordered in both its free and bound states, enabling aspects of its structure/function relationship to be elucidated.
authors.affiliation: Program in Molecular Structure and Function, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
authors.forename: Tanja
authors.initials: T
authors.lastname: Mittag
authors.forename: Joseph
authors.initials: J
authors.lastname: Marsh
authors.forename: Alexander
authors.initials: A
authors.lastname: Grishaev
authors.forename: Stephen
authors.initials: S
authors.lastname: Orlicky
authors.forename: Hong
authors.initials: H
authors.lastname: Lin
authors.forename: Frank
authors.initials: F
authors.lastname: Sicheri
authors.forename: Mike
authors.initials: M
authors.lastname: Tyers
authors.forename: Julie D
authors.initials: JD
authors.lastname: Forman-Kay
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D018360:Crystallography, X-Ray / Q000379:methods; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000235:genetics / Q000502:physiology*; D044783:F-Box Proteins / Q000235:genetics / Q000502:physiology*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D010766:Phosphorylation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D044843:SKP Cullin F-Box Protein Ligases / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D012542:Scattering, Radiation; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013912:Threonine / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000502:physiology*
chemical_list: C080443:CDC4 protein, S cerevisiae; D018797:Cell Cycle Proteins; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D044783:F-Box Proteins; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013912:Threonine; D044843:SKP Cullin F-Box Protein Ligases; D044767:Ubiquitin-Protein Ligases
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