Detergent-free reconstitution of transmembrane proteins in giant liposomes of complex curvature by the Synthetic Membrane Transfer

Transmembrane proteins perform many crucial functions in the cell, including transfer of matter and information across the membrane. Giant Unilamellar Vesicles (GUVs) are the ideal tool for studying these processes; yet functional transmembrane protein reconstitution in GUVs still represents a bottleneck in bottom-up synthetic biology. Here, we developed a novel approach that we call Synthetic Membrane Transfer (SMT), where transmembrane proteins reconstituted into styrene-maleic acid particles in a detergent-free environment can be transferred to the GUV membrane. The SMT approach is a one-step, facile and general method that works for structurally diverse proteins, and it does not require any specific lipid or buffer composition. Moreover, the SMT is fully compatible with the Synthetic Membrane Shaper (SMS) technology, which allows to deform GUVs in a controlled fashion, obtaining dumbbell-shaped GUVs exhibiting a catenoid-like geometry. The combination of SMT and SMS results in functional reconstitution of transmembrane proteins in catenoid membrane necks. Using this approach, we demonstrate that Mic10, a component of the MICOS complex, directly senses membrane curvature and localizes at the neck of dumbbells GUVs, a geometry that recapitulates the shape of mitochondria cristae junctions. This paves the way for bottom-up reconstitution of the MICOS complex on a physiological membrane geometry.