title: The acidic transcription activator Gcn4 binds the mediator subunit Gal11/Med15 using a simple protein interface forming a fuzzy complex.
abstract: The structural basis for binding of the acidic transcription activator Gcn4 and one activator-binding domain of the Mediator subunit Gal11/Med15 was examined by NMR. Gal11 activator-binding domain 1 has a four-helix fold with a small shallow hydrophobic cleft at its center. In the bound complex, eight residues of Gcn4 adopt a helical conformation, allowing three Gcn4 aromatic/aliphatic residues to insert into the Gal11 cleft. The protein-protein interface is dynamic and surprisingly simple, involving only hydrophobic interactions. This allows Gcn4 to bind Gal11 in multiple conformations and orientations, an example of a "fuzzy" complex, where the Gcn4-Gal11 interface cannot be described by a single conformation. Gcn4 uses a similar mechanism to bind two other unrelated activator-binding domains. Functional studies in yeast show the importance of residues at the protein interface, define the minimal requirements for a functional activator, and suggest a mechanism by which activators bind to multiple unrelated targets.
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Brzovic
authors.forename: Clemens C
authors.initials: CC
authors.lastname: Heikaus
authors.forename: Leonid
authors.initials: L
authors.lastname: Kisselev
authors.forename: Robert
authors.initials: R
authors.lastname: Vernon
authors.forename: Eric
authors.initials: E
authors.lastname: Herbig
authors.forename: Derek
authors.initials: D
authors.lastname: Pacheco
authors.forename: Linda
authors.initials: L
authors.lastname: Warfield
authors.forename: Peter
authors.initials: P
authors.lastname: Littlefield
authors.forename: David
authors.initials: D
authors.lastname: Baker
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Klevit
authors.forename: Steven
authors.initials: S
authors.lastname: Hahn
mesh_terms: D050976:Basic-Leucine Zipper Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D056892:Mediator Complex / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; C058337:GAL11 protein, S cerevisiae; C501391:GCN4 protein, S cerevisiae; D056892:Mediator Complex; D029701:Saccharomyces cerevisiae Proteins