Dynamic pre-structuration of lipid nanodomain-segregating remorin proteins

Abstract

Remorins are multifunctional proteins, regulating immunity, development and symbiosis in plants. When associating to the membrane, remorins sequester specific lipids into functional membrane nanodomains. The multigenic protein family contains six groups, classified upon their protein-domain composition. Membrane targeting of remorins occurs independently from the secretory pathway. Instead, they are directed into different nanodomains depending on their phylogenetic group. All family members contain a C-terminal membrane anchor and a homo-oligomerization domain, flanked by an intrinsically disordered region of variable length at the N-terminal end. We here combined molecular imaging, Nuclear Magnetic Resonance spectroscopy, protein structure calculations and advanced molecular dynamics simulation to unveil a stable pre-structuration of coiled-coil dimers as tunable nanodomain-targeting units, containing a tunable fuzzy coat and a bar code-like positive surface charge before membrane association. These protein characteristics and the differences in structures and dynamics between C-terminal lipid anchors of the remorin groups provide a selective platform for phospholipid binding when encountering the membrane surface. Our data suggest that remorins fold in the cytosol with the N-terminal disordered region as a fuzzy structural ensemble around a dimeric anti-parallel coiled-coil core containing a symmetric interface motif reminiscent of a hydrophobic Leucine zipper. The charge distribution, the intrinsic curvature in dimeric coiled-coil remorins, and their domain geometry would confer distinctive membrane association profiles. The lipid-binding of the C-terminal creates avidity through multivalent electrostatic interactions between anionic lipid headgroups and the positively charged dimer surface suggesting a clip-and-divide mechanism to selectively segregate lipid-protein nanodomains.