Structural insights into photosystem II assembly (Nature Plants)

Photosystem II is a multisubunit enzyme complex in the thylakoid membranes of plant, algae, and cyanobacteria. Here, Zebret et al. used cryo-electron microscopy to produce high-resolution structural information of the intermediate complexes involved in the biogenesis and assembly of photosystem II from the cyanobacterium Thermosynechococcus elongatus. This study shows how the spatiotemporally synchronized biogenesis process is facilitated by a network of assembly factors, particularly Psb27, Psb28 and Psb34, and reveals an important transition phase before the activation of the oxygen evolving complex (OEC). At the future site where the OEC will bind, there is a single positively charged ion that coordinates with the three amino acids Asp170, Glu189 and His332 of D1. As the authors suggest, this site “seems to be prepared to accept the Mn4CaO5 cluster, as indicated by the similarities in side-chain positioning.” (Summary by Arun K. Shanker @arunshanker) Nature Plants 10.1038/s41477-021-00895-0