Energy transfer

Physics

Photosystem

Crystallography

Biology

Gene

Thylakoid

Electron transfer

Biophysics

Photosystem I

Photosynthesis

Chemical physics

Chemistry

Light-harvesting complex

Chlorophyll a

Quantum mechanics

Biochemistry

Chloroplast

Photochemistry

Photosystem II

Excitation

Science

Plants regulate photosynthetic light harvesting to maintain balanced energy flux into photosystems I and II (PSI and PSII). Under light conditions favoring PSII excitation, the PSII antenna, light-harvesting complex II (LHCII), is phosphorylated and forms a supercomplex with PSI core and the PSI antenna, light-harvesting complex I (LHCI). Both LHCI and LHCII then transfer excitation energy to the PSI core. We report the structure of maize PSI-LHCI-LHCII solved by cryo-electron microscopy, revealing the recognition site between LHCII and PSI. The PSI subunits PsaN and PsaO are observed at the PSI-LHCI interface and the PSI-LHCII interface, respectively. Each subunit relays excitation to PSI core through a pair of chlorophyll molecules, thus revealing previously unseen paths for energy transfer between the antennas and the PSI core.

Structure of the maize photosystem I supercomplex with light-harvesting complexes I and II