title: Single-molecule FRET reveals hidden complexity in a protein energy landscape.
abstract: Here, using single-molecule FRET, we reveal previously hidden conformations of the ankyrin-repeat domain of AnkyrinR, a giant adaptor molecule that anchors integral membrane proteins to the spectrin-actin cytoskeleton through simultaneous binding of multiple partner proteins. We show that the ankyrin repeats switch between high-FRET and low-FRET states, controlled by an unstructured "safety pin" or "staple" from the adjacent domain of AnkyrinR. Opening of the safety pin leads to unravelling of the ankyrin repeat stack, a process that will dramatically affect the relative orientations of AnkyrinR binding partners and, hence, the anchoring of the spectrin-actin cytoskeleton to the membrane. Ankyrin repeats are one of the most ubiquitous molecular recognition platforms in nature, and it is therefore important to understand how their structures are adapted for function. Our results point to a striking mechanism by which the order-disorder transition and, thereby, the activity of repeat proteins can be regulated.
authors.affiliation: MRC Cancer Cell Unit, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 0XZ, UK; Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
authors.forename: Maksym
authors.initials: M
authors.lastname: Tsytlonok
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
authors.forename: Shehu M
authors.initials: SM
authors.lastname: Ibrahim
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
authors.forename: Pamela J E
authors.initials: PJE
authors.lastname: Rowling
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
authors.forename: Wenshu
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, Campus Cartuja, University of Granada, 18071 Granada, Spain.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Ruedas-Rama
authors.affiliation: Department of Physical Chemistry, Faculty of Pharmacy, Campus Cartuja, University of Granada, 18071 Granada, Spain.
authors.forename: Angel
authors.initials: A
authors.lastname: Orte
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK. Electronic address: dk10012@cam.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Klenerman
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK; Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK. Electronic address: lsi10@cam.ac.uk.
authors.forename: Laura S
authors.initials: LS
authors.lastname: Itzhaki
mesh_terms: D017089:Ankyrin Repeat / Q000235:genetics; D017487:Ankyrins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D017434:Protein Structure, Tertiary / Q000235:genetics
chemical_list: C110202:ANK1 protein, human; D017487:Ankyrins; D050505:Mutant Proteins