title: Membrane-induced folding of the cAMP-regulated phosphoprotein endosulfine-alpha.
abstract: Endosulfine-alpha (ENSA) is a 121-residue cAMP-regulated phosphoprotein, originally identified as an endogenous regulator of ATP-sensitive potassium channels. ENSA has been implicated in the regulation of insulin secretion, and expression of ENSA is decreased in brains of both Alzheimer's disease (AD) and Down's syndrome patients. We recently described membrane-dependent interactions between ENSA and the Parkinson's disease associated protein alpha-synuclein. Here we characterize the conformational change in ENSA that occurs upon binding to membranes. Secondary chemical shift analysis demonstrates formation of four helices in the lipid-bound state that are not present in the absence of lipid. The helical structure is maintained in several different lipid mimetics (sodium dodecyl sulfate, dodecyl phosphocholine, lyso 1-palmitoyl phosphatidylglycerol, and phospholipid vesicles). Introduction of a mutation (S109E) to mimic PKA phosphorylation of ENSA leads to a perturbation of the fourth helix and disrupts the interaction with alpha-synuclein. These data establish ENSA as an intrinsically unstructured protein that adopts a stable structure upon membrane binding, properties it shares with its binding partner alpha-synuclein.
authors.affiliation: Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Boettcher
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Hartman
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Ladror
authors.forename: Zhi
authors.initials: Z
authors.lastname: Qi
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Woods
authors.forename: Julia M
authors.initials: JM
authors.lastname: George
authors.forename: Chad M
authors.initials: CM
authors.lastname: Rienstra
mesh_terms: D040761:Biomimetic Materials / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006017:Glycolipids / Q000378:metabolism / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism / Q000494:pharmacology; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects; D017510:Protein Folding; D017433:Protein Structure, Secondary / Q000187:drug effects; D012967:Sodium Dodecyl Sulfate / Q000378:metabolism / Q000494:pharmacology; D051844:alpha-Synuclein / Q000378:metabolism
chemical_list: D006017:Glycolipids; D007295:Inositol Phosphates; D036341:Intercellular Signaling Peptides and Proteins; C111513:LPPG glycoinositolphosphoceramide; D008823:Micelles; D010455:Peptides; D010743:Phospholipids; D010750:Phosphoproteins; D051844:alpha-Synuclein; C075663:endosulfine; D012967:Sodium Dodecyl Sulfate; D017868:Cyclic AMP-Dependent Protein Kinases