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Title: Supercharging Prions via Amyloid‐Selective Lysine Acetylation
Abstract

Repulsive electrostatic forces between prion‐like proteins are a barrier against aggregation. In neuropharmacology, however, a prion's net charge (Z) is not a targeted parameter. Compounds that selectively boost prionZremain unreported. Here, we synthesized compounds that amplified the negative charge of misfolded superoxide dismutase‐1 (SOD1) by acetylating lysine‐NH3+in amyloid‐SOD1, without acetylating native‐SOD1. Compounds resembled a “ball and chain” mace: a rigid amyloid‐binding “handle” (benzothiazole, stilbene, or styrylpyridine); an aryl ester “ball”; and a triethylene glycol chain connecting ball to handle. At stoichiometric excess, compounds acetylated up to 9 of 11 lysine per misfolded subunit (ΔZfibril=−8100 per 103subunits). Acetylated amyloid‐SOD1 seeded aggregation more slowly than unacetylated amyloid‐SOD1 in vitro and organotypic spinal cord (these effects were partially due to compound binding). Compounds exhibited reactivity with other amyloid and non‐amyloid proteins (e.g., fibrillar α‐synuclein was peracetylated; serum albumin was partially acetylated; carbonic anhydrase was largely unacetylated).

 
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NSF-PAR ID:
10231517
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Angewandte Chemie
Volume:
133
Issue:
27
ISSN:
0044-8249
Page Range / eLocation ID:
p. 15196-15206
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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    Repulsive electrostatic forces between prion‐like proteins are a barrier against aggregation. In neuropharmacology, however, a prion's net charge (Z) is not a targeted parameter. Compounds that selectively boost prionZremain unreported. Here, we synthesized compounds that amplified the negative charge of misfolded superoxide dismutase‐1 (SOD1) by acetylating lysine‐NH3+in amyloid‐SOD1, without acetylating native‐SOD1. Compounds resembled a “ball and chain” mace: a rigid amyloid‐binding “handle” (benzothiazole, stilbene, or styrylpyridine); an aryl ester “ball”; and a triethylene glycol chain connecting ball to handle. At stoichiometric excess, compounds acetylated up to 9 of 11 lysine per misfolded subunit (ΔZfibril=−8100 per 103subunits). Acetylated amyloid‐SOD1 seeded aggregation more slowly than unacetylated amyloid‐SOD1 in vitro and organotypic spinal cord (these effects were partially due to compound binding). Compounds exhibited reactivity with other amyloid and non‐amyloid proteins (e.g., fibrillar α‐synuclein was peracetylated; serum albumin was partially acetylated; carbonic anhydrase was largely unacetylated).

     
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    The degree by which metalloproteins partially regulate net charge (Z) upon electron transfer (ET) was recently measured for the first time using “protein charge ladders” of azurin, cytochrome c, and myoglobin [Angew. Chem. Int. Ed.2018,57(19), 5364–5368;Angew. Chem.2018,130, 5462–5466]. Here, we show that Cu, Zn superoxide dismutase (SOD1) is unique among proteins in its ability to resist changes in net charge upon single ET (e.g., ΔZET(SOD1)=0.05±0.08 per electron, compared to ΔZET(Cyt‐c)=1.19±0.02). This total regulation of net charge by SOD1 is attributed to the protonation of the bridging histidine upon copper reduction, yielding redox centers that are isoelectric at both copper oxidation states. Charge regulation by SOD1 would prevent long range coulombic perturbations to residue pKa’s upon ET at copper, allowing SOD1’s “electrostatic loop” to attract superoxide with equal affinity (at both redox states of copper) during diffusion‐limited reduction and oxidation of superoxide.

     
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    Basic Protocol 1: Labeling HAT protein substrates with azide/alkyne‐biotin

    Alternate Protocol: Labeling protein substrates of HATs with azide/alkyne‐TAMRA for in‐gel visualization

    Support Protocol 1: Expression and purification of HAT mutants

    Support Protocol 2: Synthesis of Ac‐CoA surrogates

    Basic Protocol 2: Streptavidin enrichment of biotinylated HAT substrates

    Basic Protocol 3: Chemoproteomic identification of HAT substrates

    Basic Protocol 4: Validation of specific HAT substrates with western blotting

     
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