Psb27, a Cyanobacterial Lipoprotein, Is Involved in the Repair Cycle of Photosystem II

摘要

Photosystem II (PSII) performs one of the key reactions on our planet: the light-driven oxidation of water. This fundamental but very complex process requires PSII to act in a highly coordinated fashion. Despite detailed structural information on thefully assembled PSII complex, the dynamic aspects of formation, processing, turnover, and degradation of PSII with at least 19 subunits and various cofactors are still not fully understood. Transient complexes are especially difficult to characterize dueto low abundance, potential heterogeneity, and instability. Here, we show that Psb27 is involved in the assembly of the water-splitting site of PSII and in the turnover of the complex. Psb27 is a bacterial lipoprotein with a specific lipid modificationas shown by matrix-assisted laser-desorption ionization time of flight mass spectrometry. The combination of HPLC purification of four different PSII subcomplexes and 15N pulse label experiments revealed that lipoprotein Psb27 is part of a preassembled PSII subcomplex that represents a distinct intermediate in the repair cycle of PSII.