title: The disordered C-terminus of the RNA polymerase II phosphatase FCP1 is partially helical in the unbound state.
abstract: Intrinsically disordered proteins (IDPs) lack unique 3D structures under native conditions and yet retain critical functions. Recycling of RNA Polymerase II after transcription is promoted by an interaction between the winged helix domain of RAP74, a component of the general transcription factor IIF (TFIIF), and the C-terminus of the TFIIF-associating CTD phosphatase (FCP1). Sixteen residues from the C-terminus of FCP1 form an α-helix in the complex, but the protein is otherwise agreed in the literature to be intrinsically disordered. Here we show through CD and recently developed carbon-detected NMR that, although FCP1 is intrinsically disordered, the above 16 residues composing the RAP74 binding surface form nascent α-helical structure in the unbound state. We further show retention of general FCP1 disorder and the nascent helical content in HeLa extract, establishing cellular relevance. The conformational bias observed leads to a mechanistic proposal for FCP1's transition from a disordered ensemble to an ordered conformation upon binding.
authors.affiliation: Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, USA. cwl137@psu.edu
authors.forename: Chad W
authors.initials: CW
authors.lastname: Lawrence
authors.forename: Alain
authors.initials: A
authors.lastname: Bonny
authors.forename: Scott A
authors.initials: SA
authors.lastname: Showalter
mesh_terms: D002457:Cell Extracts / Q000737:chemistry; D002942:Circular Dichroism; D003911:Dextrans / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular; D009687:Nuclear Proteins / Q000737:chemistry*; D010749:Phosphoprotein Phosphatases / Q000737:chemistry*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D019473:Transcription Factors, TFII / Q000737:chemistry; D014508:Urea / Q000737:chemistry
chemical_list: D002457:Cell Extracts; D003911:Dextrans; D009687:Nuclear Proteins; D019473:Transcription Factors, TFII; D014508:Urea; C108580:CTDSP2 protein, human; D010749:Phosphoprotein Phosphatases; C056604:transcription factor TFIIF