Dynamical and allosteric regulation of photoprotection in light harvesting complex II

Thermal/acidity triggered formation of a pair of local α-helices from 310-helix E/loop and the C-terminal coil connecting helix D in the neighboring monomer induces a scissoring motion of transmembrane helix A and B, shifting the conformational equilibrium to a more open state as a protein switch. The dynamical and allosteric conformation change leads to close contacts between carotenoid lutein 1 and chlorophyll pigment 612, leading to an increased electronic coupling and facilitating the fluorescence quenching.