Modern mass spectrometry‑based lipidomics allows us to catalogue the lipid constituents of biological membranes with remarkable precision, yet we still struggle to explain how these molecules work together to shape membrane organization and function. A central challenge lies in a fundamental duality between lipid chemical specificity and physical collectivity. Individual lipid species interact specifically with proteins as ligands, allosteric modulators, or structural scaffolds, while at the same time lipids act collectively to define bulk membrane properties—such as fluidity, thickness, and curvature stress—that modulate protein function without specific molecular recognition.
We address this challenge by focusing on membrane asymmetry—the unequal distribution of lipids across the bilayer—a defining feature of plasma membranes. Using a bottom‑up strategy, we construct plasma membrane mimics from a small, chemically well‑defined set of lipid species, selected on the basis of their headgroup and acyl‑chain structure. We fabricate organelle‑sized asymmetric lipid vesicles and quantify their bulk physical properties using small‑angle scattering and complementary biophysical methods. These measurements reveal that the collective properties of one leaflet can modulate those of the opposite leaflet, sometimes in non‑intuitive ways, highlighting asymmetry‑mediated interleaflet coupling.
To link asymmetry to function, we reconstituted the outer membrane phospholipase A (OmpLA) into asymmetric bilayers and quantified its activity. Lipid asymmetry strongly regulates OmpLA: activity is reduced in charge‑neutral asymmetric membranes but enhanced in charged asymmetric environments. Moreover, ions further tune enzymatic activity via interactions with lipid headgroups. Together, our results are consistent with allosteric modulation of protein function by changes in lateral stress profiles and show how chemically resolved lipid composition and leaflet‑specific lipid distribution converge to control membrane protein function, underscoring the need to integrate lipidomics with physical measurements of membrane organization.