Cellularmembrane-like structure of tubular-linked liposome network

Expression, purification, and characterization of single-species of membrane protein are one of the most important technologies in post-genome era. Especially membrane proteins are difficult to isolate and purify with keeping their function. We engaged to study direct reconstitution of cell-free synthesized membrane proteins to giant liposomes. Recently we reported that the spontaneous formation of the three-dimensional lipid tubular network in the presence of various gangliosides or cholesterol. Here we report the experimental trial to obtain the fixed liposome-network with functional membrane proteins. As a model membrane protein, cytochrome-b5 was adopted. In the presence of liposomes, the expressed membrane proteins were directly and effectively displayed on the liposomal surface without aggregation. The proteo-liposomes were fixed to tubular-connected networks by adding gangliosides. The network formation process in the agarose gel was directly observed by fluorescent microscopy. Hemispheric liposomes changed their form to the tubular-networks in the gelation process. The stable lipid nanotube network can be used for constructing a biochemical micro-reactor to analyze membrane protein functions.