title: Quaternary structure of KATP channel SUR2A nucleotide binding domains resolved by synchrotron radiation X-ray scattering.
abstract: Heterodimeric nucleotide binding domains NBD1/NBD2 distinguish the ATP-binding cassette protein SUR2A, a recognized regulatory subunit of cardiac ATP-sensitive K(+) (K(ATP)) channels. The tandem function of these core domains ensures metabolism-dependent gating of the Kir6.2 channel pore, yet their structural arrangement has not been resolved. Here, purified monodisperse and interference-free recombinant particles were subjected to synchrotron radiation small-angle X-ray scattering (SAXS) in solution. Intensity function analysis of SAXS profiles resolved NBD1 and NBD2 as octamers. Implemented by ab initio simulated annealing, shape determination prioritized an oblong envelope wrapping NBD1 and NBD2 with respective dimensions of 168x80x37A(3) and 175x81x37A(3) based on symmetry constraints, validated by atomic force microscopy. Docking crystal structure homology models against SAXS data reconstructed the NBD ensemble surrounding an inner cleft suitable for Kir6.2 insertion. Human heart disease-associated mutations introduced in silico verified the criticality of the mapped protein-protein interface. The resolved quaternary structure delineates thereby a macromolecular arrangement of K(ATP) channel SUR2A regulatory domains.
authors.affiliation: Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Departments of Medicine, Molecular Pharmacology and Experimental Therapeutics, and Medical Genetics, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Sungjo
authors.initials: S
authors.lastname: Park
authors.forename: Andre
authors.initials: A
authors.lastname: Terzic
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002942:Circular Dichroism; D006801:Humans; D051379:Mice; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000235:genetics; D020836:Protein Structure, Quaternary; D011955:Receptors, Drug / Q000737:chemistry* / Q000235:genetics; D053838:Scattering, Small Angle; D064233:Sulfonylurea Receptors; D017356:Synchrotrons; D014961:X-Ray Diffraction
chemical_list: C577510:ABCC9 protein, human; D018528:ATP-Binding Cassette Transporters; C577511:Abcc9 protein, mouse; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors