Rubber particle proteins, HbREF and HbSRPP, show different interactions with model membranes

Abstract

The biomembrane surrounding rubber particles from the hevea latex is well known for its content of numerous allergen proteins. HbREF (Hevb1) and HbSRPP (Hevb3) are major components, linked on rubber particles, and they have been shown to be involved in rubber synthesis or quality (mass regulation), but their exact function is still to be determined. In this study we highlighted the different modes of interactions of both recombinant proteins with various membrane models (lipid monolayers, liposomes or supported bilayers, and multilamellar vesicles) to mimic the latex particle membrane. We combined various biophysical methods (polarization-modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS)/ellipsometry, attenuated-total reflectance Fourier-transform infrared (ATR-FTIR), solid-state nuclear magnetic resonance (NMR), plasmon waveguide resonance (PWR), fluorescence spectroscopy) to elucidate their interactions. Small rubber particle protein (SRPP) shows less affinity than rubber elongation factor (REF) for the membranes but displays a kind of "covering" effect on the lipid headgroups without disturbing the membrane integrity. Its structure is conserved in the presence of lipids. Contrarily, REF demonstrates higher membrane affinity with changes in its aggregation properties, the amyloid nature of REF, which we previously reported, is not favored in the presence of lipids. REF binds and inserts into membranes. The membrane integrity is highly perturbed, and we suspect that REF is even able to remove lipids from the membrane leading to the formation of mixed micelles. These two homologous proteins show affinity to all membrane models tested but neatly differ in their interacting features. This could imply differential roles on the surface of rubber particles.

Lipid Droplet-Associated Proteins (LDAPs) Are Required for the Dynamic Regulation of Neutral Lipid Compartmentation in Plant Cells

“…2A); thus, it appears that the entire protein sequence is required for high-fidelity association with LDs. This is somewhat different from the results for SRPP, where studies have shown that deletion of the C-terminal half of the protein did not abolish a capability to interact with membranes (Berthelot et al, 2014c), although these studies were conducted using purified proteins and membranes in vitro and, thus, the observed differences might be due to the experimental approaches employed.…”

Production and characterization of natural rubber–Ca/P blends for biomedical purposes

“…3(a) suggests a random and homogeneous distribution of these components over the NR particle embedded in the bulk of the polymeric matrix. In contradiction with previous studies reported in the literature, where models for the NR particles have been proposed, considering the proteins and phospholipids having a heterogeneous distribution, with protein/phospholipid agglomerates on the NR particle surface [34,37].…”

Hevea brasiliensis REF (Hev b 1) and SRPP (Hev b 3): An overview on rubber particle proteins

“…4A), different structures were provided using ATR-FTIR for both proteins in solution (Fig. 4B) or in presence of model membranes [20]. In solution, REF was able to form amyloid fibres and aggregates rich in b-sheets, whereas SRPP showed all the characteristics of a more globular protein also able of auto-assembly [26].…”

“…This membrane is fluid and permeable [16,20e22]. For example, this membrane was easily marked by incorporation of DMPC-rhodamine and the polyisoprene core stained by Nile red [20]. The thickness of this monolayer has been estimated to be around 1.5e4.0 nm [16,17,21,23].…”