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).