Formation of lysozyme oligomers at model cell membranes monitored with sum frequency generation spectroscopy

Izabela Irena Rzeznicka, R. Pandey, M. Schleeger, M. Bonn, T. Weidner

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

A growing number of studies suggest that the formation of toxic oligomers, precursors of amyloid fibrils, is initiated at the cell membrane and not in the cytosolic compartments of the cell. Studies of membrane-induced protein oligomerization are challenging due to the difficulties of probing small numbers of proteins present at membrane surfaces. Here, we employ surface-sensitive vibrational sum frequency generation (VSFG) to investigate the secondary structure of lysozyme at the surface of lipid monolayers. We investigate lysozyme aggregation at negatively charged 1,2-dipalmitoyl-sn-glycero-3- (phospho-rac-1-glycerol) (DPPG) lipid monolayers under different pH conditions. The changes in the molecular vibrations of lipids, proteins, and water as a function of pH and surface pressure allow us to simultaneously monitor details of the conformation state of lysozyme, the organization of lipids, and the state of lipid-bound water. At pH = 6 lysozyme induces significant disordering of the lipid layer, and it exists in two states: a monomeric state with a predominantly α-helix content and an oligomeric (za-mer) state. At pH ≤ 3, all membrane-bound lysozyme self-associates into oligomers characterized by an antiparallel β-sheet structure. This is different from the situation in bulk solution, for which circular dichroism (CD) shows that the protein maintains an α-helix conformation, under both neutral and acidic pH conditions. The transition from monomers to oligomers is also associated with a decreased hydration of the lipid monolayer resulting in an increase of the lipid acyl chains ordering. The results indicate that oligomerization requires cooperative action between lysozyme incorporated into the lipid membrane and peripherally adsorbed lysozyme and is associated with the membrane dehydration and lipid reorganization. Membrane-bound oligomers with antiparallel β-sheet structure are found to destabilize lipid membranes.

Original languageEnglish
Pages (from-to)7736-7744
Number of pages9
JournalLangmuir
Volume30
Issue number26
DOIs
Publication statusPublished - 2014 Jul 8
Externally publishedYes

Fingerprint

lysozyme
Cell membranes
Muramidase
oligomers
Oligomers
Lipids
lipids
Enzymes
Spectroscopy
spectroscopy
membranes
Membranes
Proteins
Monolayers
Oligomerization
proteins
Membrane Lipids
Conformations
helices
Molecular vibrations

ASJC Scopus subject areas

  • Electrochemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Materials Science(all)
  • Spectroscopy
  • Medicine(all)

Cite this

Formation of lysozyme oligomers at model cell membranes monitored with sum frequency generation spectroscopy. / Rzeznicka, Izabela Irena; Pandey, R.; Schleeger, M.; Bonn, M.; Weidner, T.

In: Langmuir, Vol. 30, No. 26, 08.07.2014, p. 7736-7744.

Research output: Contribution to journalArticle

Rzeznicka, Izabela Irena ; Pandey, R. ; Schleeger, M. ; Bonn, M. ; Weidner, T. / Formation of lysozyme oligomers at model cell membranes monitored with sum frequency generation spectroscopy. In: Langmuir. 2014 ; Vol. 30, No. 26. pp. 7736-7744.
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