The interaction of equine lysozyme: oleic acid complexes with lipid membranes suggests a cargo off-loading mechanism
2010 (English)In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 398, no 2, 351-361 p.Article in journal (Refereed) Published
The normal function of equine lysozyme (EL) is the hydrolysis of peptidoglycan residues of bacterial cell walls. EL is closely related to alpha-lactalbumins with respect to sequence and structure and further possesses the calcium binding site of alpha-lactalbumins. Recently, EL multimeric complexes with oleic acids (ELOA) were shown to possess tinctorial and morphological properties, similar to amyloidal aggregates, and to be cytotoxic. ELOA's interactions with phospholipid membranes appears to be central to its biological action, similar to human alpha-lactalbumin made lethal to tumor cells (HAMLET). Here, we describe the interaction of ELOA with phospholipid membranes. Confocal scanning laser microscopy shows that ELOA, but not native EL, accumulates on the surface of giant unilamellar vesicles, without inducing significant membrane permeability. Quartz crystal microbalance with dissipation (QCM-D) data indicated an essentially non-disruptive binding of ELOA to supported lipid bilayers, leading to formation of highly dissipative and "soft" lipid membrane; at higher concentrations of ELOA, the lipid membrane desorbs from the surface probably as bilayer sheets of vesicles. This membrane rearrangement occurred to a similar extent when free oleic acid (OA) was added, but not when free OA was removed from ELOA by prior incubation with BSA, emphasizing the role of OA in this process. NMR data indicated an equilibrium between free and bound OA which shifts towards free OA as ELOA is progressively diluted indicating that OA is relatively loosely bound. Activity measurements together with fluorescence spectroscopy and circular dichroism suggested a conversion of ELOA toward a more native-like state on interaction with lipid membranes, although complete refolding was not observed. Altogether, these results suggest that ELOA may act as an OA carrier and facilitate OA transfer to the membrane. ELOA's properties illustrate that protein folding variants may possess specific functional properties distinct from the native protein. Abbreviations QCM-D, Quartz crystal microbalance with dissipation; CD, Circular dichroism; EL, equine lysozyme; ELOA, EL complex with oleic acid; OA, oleic acid, CSLM, Confocal scanning laser microscopy, Df, dissipation-frequency.
Place, publisher, year, edition, pages
Elsevier, 2010. Vol. 398, no 2, 351-361 p.
confocal laser scanning microscopy, equine lysozyme, oleic acid, supported lipid bilayers, quartz crystal microbalance with dissipation
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
IdentifiersURN: urn:nbn:se:umu:diva-32568DOI: 10.1016/j.jmb.2010.03.012ISI: 000277664800013PubMedID: 20227419OAI: oai:DiVA.org:umu-32568DiVA: diva2:304132