1. Intra- and Intersubunit Ion-Pair Interactions Determine the Ability of Apolipoprotein C-II Mutants To Form Hybrid Amyloid Fibrils.
- Author
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Todorova N, Zlatic CO, Mao Y, Yarovsky I, Howlett GJ, Gooley PR, and Griffin MD
- Subjects
- Amyloid genetics, Amyloid metabolism, Amyloidogenic Proteins genetics, Amyloidogenic Proteins metabolism, Apolipoprotein C-II genetics, Apolipoprotein C-II metabolism, Aspartic Acid chemistry, Aspartic Acid metabolism, Gene Expression, Humans, Lysine chemistry, Lysine metabolism, Molecular Dynamics Simulation, Mutation, Protein Conformation, alpha-Helical, Protein Conformation, beta-Strand, Protein Subunits genetics, Protein Subunits metabolism, Recombinant Proteins chemistry, Recombinant Proteins genetics, Recombinant Proteins metabolism, Static Electricity, Amyloid chemistry, Amyloidogenic Proteins chemistry, Apolipoprotein C-II chemistry, Protein Subunits chemistry
- 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.
- Published
- 2017
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