Mechanisms of lipid recognition in methyl-α-cyclodextrin-mediated lipid exchange for the design of plant plasma membrane models.

Abstract

Asymmetric liposomes that mimic plant plasma membranes (PPM) have not been developed so far, despite the impact of the PPM's transverse lipid distribution on its biophysical properties and its involvement in many biological processes. The cyclodextrin-mediated exchange of PLPC (16:0-18:2 PC) and POPC (16:0-18:1 PC), two lipids that are strongly represented in the PPM, can potentially be used to achieve an asymmetry in leaflet composition mimicking that of the PPM. In this work, we use molecular free energy simulations to study the interaction of methyl-α-cyclodextrin with these two lipids. We show that kinetic barriers to the sliding of the CD along the linoleoyl chain of PLPC, due to the locking effect of curved linoleoyl chain conformations, can extend the lifetime of PLPC/CD complexes comparared to POPC. While sufficient to discriminate PLPC from POPC, the associated free energy barriers show that CD uptake and release is feasible for both lipids within the typical timescales of in vitro experiments. The preferred positions of the CD on the lipid chains also condition the ability to recruit additional CDs for better shielding of the lipid tails from water. We discuss how this subtle kinetic balance relates to previous experimental results and its implication for the design of PPM models via lipid exchange.

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