title: Intra- and Intersubunit Ion-Pair Interactions Determine the Ability of Apolipoprotein C-II Mutants To Form Hybrid Amyloid Fibrils.
abstract: The apolipoprotein family is structurally defined by amphipathic α-helical regions that interact with lipid surfaces. In the absence of lipid, human apolipoprotein (apo) C-II also forms well-defined amyloid fibrils with cross-β structure. Formation of this β-structure is accompanied by the burial of two charged residues, K30 and D69, that form an ion-pair within the amyloid fibril core. Molecular dynamics (MD) simulations indicate these buried residues form both intra- and intersubunit ion-pair interactions that stabilize the fibril. Mutations of the ion-pair (either K30D or D69K) reduce fibril stability and prevent fibril formation by K30D apoC-II under standard conditions. We investigated whether mixing K30D apoC-II with other mutants would overcome this loss of fibril forming ability. Co-incubation of equimolar mixtures of K30D apoC-II with wild-type, D69K, or double-mutant (K30D/D69K) apoC-II promoted the incorporation of K30D apoC-II into hybrid fibrils with increased stability. MD simulations showed an increase in the number of intersubunit ion-pair interactions accompanied the increased stability of the hybrid fibrils. These results demonstrate the important role of both intra- and intersubunit charge interactions in stabilizing apoC-II amyloid fibrils, a process that may be a key factor in determining the general ability of proteins to form amyloid fibrils.
authors.affiliation: School of Engineering, RMIT University , GPO Box 2476V, Melbourne, Victoria 3001, Australia.
authors.forename: Nevena
authors.initials: N
authors.lastname: Todorova
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne , Parkville, Victoria 3010, Australia.|Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Parkville, Victoria 3010, Australia.
authors.forename: Courtney O
authors.initials: CO
authors.lastname: Zlatic
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne , Parkville, Victoria 3010, Australia.|Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Parkville, Victoria 3010, Australia.
authors.forename: Yu
authors.initials: Y
authors.lastname: Mao
authors.affiliation: School of Engineering, RMIT University , GPO Box 2476V, Melbourne, Victoria 3001, Australia.
authors.forename: Irene
authors.initials: I
authors.lastname: Yarovsky
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne , Parkville, Victoria 3010, Australia.|Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Parkville, Victoria 3010, Australia.
authors.forename: Geoffrey J
authors.initials: GJ
authors.lastname: Howlett
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne , Parkville, Victoria 3010, Australia.|Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Parkville, Victoria 3010, Australia.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Gooley
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne , Parkville, Victoria 3010, Australia.|Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , Parkville, Victoria 3010, Australia.
authors.forename: Michael D W
authors.identifier: 0000-0001-9845-7735
authors.initials: MD
authors.lastname: Griffin
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D058227:Amyloidogenic Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D053304:Apolipoprotein C-II / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001224:Aspartic Acid / Q000737:chemistry / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D008239:Lysine / Q000737:chemistry / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D009154:Mutation; D000072756:Protein Conformation, alpha-Helical; D000072757:Protein Conformation, beta-Strand; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity
chemical_list: D000682:Amyloid; D058227:Amyloidogenic Proteins; D053304:Apolipoprotein C-II; D021122:Protein Subunits; D011994:Recombinant Proteins; D001224:Aspartic Acid; D008239:Lysine