Eukaryotic plasma membranes (PMs) are compartmentalized into functional lateral domains, including lipid-driven membrane rafts. Rafts are involved in most PM functions by selective recruitment and retention of specific proteins. However, the features that determine transmembrane protein partitioning to raft domains are unknown. We used Giant Plasma Membrane Vesicles (GPMVs) isolated directly from live cells to directly quantify the structural determinants of protein association with membrane domains. From raft affinity measurements for &gt;100 proteins, we identified three physical features of transmembrane domains (TMDs) – surface area, length, and palmitoylation – that independently affect raft partitioning. These observations were rationalized with a mechanistic, physical model that could be used to correctly predict raft affinity directly from protein sequence. These experimental insights were supported by extensive coarse-grained and atomistic molecular dynamics simulations, as well as potential of mean force calculations to describe the partitioning dynamics and energetics of transmembrane proteins. We find that partitioning between domains is determined by an interplay between protein-lipid interactions and differential lipid packing between ordered and disordered membrane phases. Specifically, we show that partitioning into ordered domains is promoted by preferential interactions between peptides and ordered lipids, as well as elastic effects mediated by hydrophobic matching between the membrane and the peptide. Conversely, ordered domain partitioning is disfavored by the tight molecular packing of the lipids therein. Thus, our combination of experimental measurements, computational models, and bioinformatic predictions establish general rules for raft partitioning of transmembrane proteins.

Structural determinants of protein partitioning into ordered membrane domains: insights from experiment and simulations

2019 Spring National Meeting

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