Figure 3.

A model for the induction of qE in C. reinhardtii. When C. reinhardtii cells are exposed to HL for several hours (A), the expression of LHCSR3 is induced (B). LHCSR3 (yellow) is then associated with the PSII-LHCII supercomplex to form the PSII-LHCII-LHCSR3 supercomplex (C). Though the PSII-LHCII-LHCSR3 supercomplex is still in a light-harvesting state under dark or LL conditions, it becomes energy-dissipative upon protonation of LHCSR3 (red; “H” denotes protonation) (E) in the acidified thylakoid lumen under HL conditions (D). DCCD-binding to LHCSR3 (yellow; “D” denotes DCCD) inhibits the conversion of PSII-LHCII-LHCSR3 supercomplex from the light-harvesting state to the energy-dissipative state (F). The crystal coordinates were obtained from the Protein Data Bank: PSII core, 3ARC; LHCII, 2NHW; and PSI-LHCI supercomplex, 2WSC.