A facile, sensitive and quantitative membrane‐binding assay for proteins

Soluble proteins that bind membranes function in numerous cellular pathways yet facile, sensitive and quantitative methods that complement and improve sensitivity of widely used liposomes‐based assays remain unavailable. Here, we describe the utility of a photoactivable fluorescent lipid as a generic reporter of protein‐membrane interactions. When incorporated into liposomes and exposed to ultraviolet (UV), proteins bound to liposomes become crosslinked with the fluorescent lipid and can be readily detected and quantitated by in‐gel fluorescence analysis. This modification obviates the requirement for high‐speed centrifugation spins common to most liposome‐binding assays. We refer to this assay as Proximity‐based Labeling of Membrane‐Associated Proteins (PLiMAP). The utility of a photoactivable fluorescent lipid as a generic reporter of protein‐membrane interactions is described. When incorporated into liposomes and exposed to UV, proteins bound to liposomes become crosslinked with the fluorescent lipid and can be readily detected and quantitated by in‐gel fluorescence analysis. We refer to this assay as Proximity‐based Labeling of Membrane‐Associated Proteins (PLiMAP).