Functional Insertion of the Light-Induced Ion Pump KR2 into Block Copolymer Membranes

Light-driven membrane proteins are attractive functional elements for biohybrid membranes, as they enable direct conversion of light energy into ion gradients. While microbial rhodopsins have been extensively studied in lipid bilayers, their controlled incorporation into synthetic polymer membranes remains challenging. Here, we investigate the reconstitution of the light-driven proton and sodium pump Krokinobacter eikastus rhodopsin 2 (KR2) into amphiphilic block copolymer membranes using a mild detergent-assisted strategy. KR2 and a C-terminal GFP fusion variant were incorporated into both solid-supported planar membranes and polymersomes under low concentrations of n-dodecyl-β-d-maltopyranoside. Membrane stability and protein incorporation were characterized using surface-sensitive and fluorescence-based techniques, while ion transport activity was assessed in polymersomes. The GFP fusion enabled quantitative assessment of membrane association and insertion behavior. Reconstituted KR2 variants retained light-driven ion transport activity in polymersomes. This straightforward approach supports the development of biohybrid systems with potential for light-driven ion transport, sensing, and energy-conversion applications.