PSII-LHCII Supercomplex Organizations in Photosynthetic Membrane by Coarse-Grained Simulation
Cheng-Kuang Lee1,2*, Chun-Wei Pao1, Berend Smit2
1Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
2Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, United States of America
* presenting author:Cheng-Kuang Lee,
Green plant photosystem II (PSII) and light-harvesting complex II (LHCII) in the stacked grana regions of thylakoid membranes can self-organize into various PSII-LHCII supercomplexes with crystalline or fluid-like supramolecular structures to adjust themselves with external stimuli such as high/low light and temperatures, rendering tunable solar light absorption spectrum and photosynthesis efficiencies. However, the mechanisms controlling the PSII-LHCII supercomplex organizations remain elusive. In this work, we constructed a coarse-grained (CG) model of the thylakoid membrane including lipid molecules and PSII-LHCII supercomplex considering association/dissociation of moderately-bound-LHCIIs. The CG interaction between CG beads were constructed based on electron microscope (EM) experimental results, and we were able to simulate the PSII-LHCII supramolecular organization of a 500 × 500 nm2 thylakoid membrane, which is compatible with experiments. Our CGMD simulations can successfully reproduce order structures of PSII-LHCII supercomplexes under different protein packing fractions, free-LHCII:PSII ratios, and temperatures, thereby providing insights into mechanisms leading to PSII-LHCII supercomplex organizations in photosynthetic membrane.

Keywords: photosynthesis, photosystem II, light-harvesting complex II, thylakoid, coarse-grained simulation