Figure1. A model of the PSII life-cycle. From Weisz et al. Front. Plant Sci. 2016.
Photosystem II (PSII) is a large membrane-protein complex that initiates photosynthesis by capturing sunlight and converting it to chemical energy, in the process splitting water into protons, electrons, and oxygen. This reaction supplies the energy to power nearly all life on Earth, and provides the oxygen that we breathe. The water-splitting reaction, the most energetically demanding in all of biology, is carried out at the active site of PSII, a Mn4CaO5 cluster (“Mn cluster”) buried deep within the complex. Active PSII is damaged frequently in vivo, particularly on the core D1 protein, as a result of the highly reactive oxidizing and reducing species that are generated near the Mn cluster and at other redox-active sites throughout the complex. Damaged PSII must be partially disassembled, a new copy of the damaged protein(s) must be inserted, and the complex must be re-assembled and photoactivated. This intricate sequence is known as the PSII “life-cycle,” and it is becoming increasingly clear that it is a complicated, tightly regulated process consisting of numerous stages, in which many external protein cofactors bind transiently to optimize the process and protect the vulnerable intermediate PSII sub-complexes. Our lab studies various stages of the PSII life-cycle. We have identified key steps during PSII assembly and have characterized the role and structural binding location of proteins that protect PSII during this process. We use a combination of genetics, biochemistry, spectroscopy, and mass spectrometry techniques to study the PSII life-cycle.
Selected project publications