Merck
  • Home
  • Search Results
  • Lysophospholipid-containing membranes modulate the fibril formation of the repeat domain of a human functional amyloid, pmel17.

Lysophospholipid-containing membranes modulate the fibril formation of the repeat domain of a human functional amyloid, pmel17.

Journal of molecular biology (2014-12-03)
Zhiping Jiang, Jennifer C Lee
ABSTRACT

Pmel17 is an important protein for pigmentation in human skin and eyes. Proteolytic fragments from Pmel17 form fibrils upon which melanin is deposited in melanosomes. The repeat domain (RPT) derived from Pmel17 only forms fibrils under acidic melanosomal conditions. Here, we examined the effects of lipids on RPT aggregation to explore whether intramelanosomal vesicles can facilitate fibrillogenesis. Using transmission electron microscopy, circular dichroism, and fluorescence spectroscopy, we monitored fibril formation at the ultrastructural, secondary conformational, and local levels, respectively. Phospholipid vesicles and lysophospholipid (lysolipid) micelles were employed as membrane mimics. The surfactant-like lysolipids are particularly pertinent due to their high content in melanosomal membranes. Interestingly, RPT aggregation kinetics were influenced only by lysolipid-containing phospholipid vesicles. While both vesicles containing either anionic lysophosphatidylglycerol (LPG) or zwitterionic lysophosphatidylcholine (LPC) stimulate aggregation, LPG exerted a greater effect on reducing the apparent nucleation time. A detailed comparison showed distinct behaviors of LPG versus LPC monomers and micelles plausibly originating from their headgroup hydrogen bonding capabilities. Acceleration and retardation of aggregation were observed for LPG monomers and micelles, respectively. Because a specific interaction between LPG and RPT was identified by intrinsic W423 fluorescence and induced α-helical structure, it is inferred that binding of LPG near the C-terminal amyloid core initiates intermolecular association, whereas stabilization of α-helical conformation inhibits β-sheet formation. Contrastingly, LPC promotes RPT aggregation at both submicellar and micellar concentrations via non-specific binding with undetectable secondary structural change. Our findings suggest that protein-lysolipid interactions within melanosomes may regulate amyloid formation in vivo.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Imidazole, ReagentPlus®, 99%
Sigma-Aldrich
MOPS, BioUltra, for molecular biology, ≥99.5% (T)
Sigma-Aldrich
MOPS, BioPerformance Certified, suitable for cell culture, ≥99.5% (titration)
Sigma-Aldrich
Imidazole, BioUltra, ≥99.5% (GC)
Sigma-Aldrich
Imidazole, puriss. p.a., ≥99.5% (GC)
Sigma-Aldrich
Imidazole, BioUltra, for molecular biology, ≥99.5% (GC)
Sigma-Aldrich
Imidazole, for molecular biology, ≥99% (titration)
Sigma-Aldrich
Imidazole, ACS reagent, ≥99% (titration)
Sigma-Aldrich
Imidazole, ≥99% (titration), crystalline
Sigma-Aldrich
MOPS, BioXtra, ≥99.5% (titration)
Sigma-Aldrich
MOPS, ≥99.5% (titration)
Imidazole, European Pharmacopoeia (EP) Reference Standard
Ondansetron impurity E, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
MOPS, Vetec, reagent grade
Sigma-Aldrich
Imidazole, Vetec, reagent grade, 98%
Supelco
Imidazole, Pharmaceutical Secondary Standard; Certified Reference Material
SAFC
MOPS
USP
Imidazole, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
MOPS, anhydrous, free-flowing, Redi-Dri, ≥99.5%
Sigma-Aldrich
Imidazole, anhydrous, free-flowing, Redi-Dri, ACS reagent, ≥99%
Sigma-Aldrich
Imidazole, ReagentPlus®, 99%, Redi-Dri, free-flowing
Sigma-Aldrich
Imidazole, for molecular biology, ≥99% (titration), free-flowing, Redi-Dri
Sigma-Aldrich
Sodium acetate trihydrate, meets USP testing specifications
Sigma-Aldrich
Sodium acetate trihydrate, BioXtra, ≥99.0%
Sigma-Aldrich
Sodium acetate trihydrate, ACS reagent, ≥99%
Sigma-Aldrich
Sodium acetate trihydrate, ReagentPlus®, ≥99.0%
Sigma-Aldrich
Sodium acetate trihydrate, puriss., meets analytical specification of Ph. Eur., BP, USP, FCC, E262, 99.0-101.0% (calc. to the dried substance), ≤0.00002% Al
Sigma-Aldrich
Sodium acetate trihydrate, Vetec, reagent grade, 99%
Sigma-Aldrich
2-Oleoyl-1-palmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt, ≥98.0% (TLC)
Sigma-Aldrich
Sodium acetate trihydrate, BioUltra, ≥99.5% (NT)