Mechanism of Budded Virus Envelope Fusion into a Planar Bilayer Lipid Membrane on a SiO₂ Substrate

Artificial planar bilayer lipid membranes (BLMs) are simple models of cellular systems under physically and chemically controlled conditions, and they have been used to investigate membrane protein activity. Baculovirus-budded virus (BV) systems can express recombinant membrane proteins. In this study, aiming for membrane protein reconstitution, we examined the fusion of BVs containing recombinant membrane proteins into artificial planar BLMs on a Si microwell substrate. BV fusion with the BLMs depended on the pH of the solution, and it was enhanced at lower pH. Based on fluorescence recovery after photobleaching (FRAP) measurement, the fusion state of BVs was evaluated, and full fusion at low pH was confirmed. The fluorescent labeling the membrane proteins was also observed in the freestanding part of the BLMs as well as in the supported part. These results demonstrate the effectiveness of BLMs as a platform to examine detailed fusion dynamics of BVs. Furthermore, this study revealed that the fusion of BVs is a promising method for reconstituting membrane proteins to artificial freestanding BLMs for the development of biodevices with which we can examine membrane protein activity.