Year: 2024
Type: article
Abstract: Photosystem II (PSII) catalyzes the light-driven charge separation and water oxidation reactions of photosynthesis. Eukaryotic PSII core is usually associated with membrane-embedded light-harvesting antennae, which greatly increase the absorbance cross-section of the core. The peripheral antennae in different phototrophs vary considerably in protein composition and arrangement. Photosynthetic cryptophytes possess chlorophyll a/c binding proteins (CACs) that serve as their antennae. How these CACs assemble with the PSII core remains unclear. Here, we report the 2.57-Å resolution structure of cryptophyte PSII-CAC purified from cells at nitrogen-limited stationary growth phase. We show that each monomer of the PSII homodimer contains a core complex, six chlorophyll a/c binding proteins (CACs) and a previously unseen chlorophyll-binding protein (termed CAL-II). Six CACs are arranged as a double-layered arc-shaped non-parallel belt, and two such belts attach to the dimeric core from opposite sides. The CAL-II simultaneously interacts with a number of core subunits and five CACs. The distinct organization of CACs and the presence of CAL-II may play a critical role in stabilizing the dimeric PSII-CAC complex under stress conditions. Our study provides mechanistic insights into the assembly and function of the PSII-CAC complex as well as the possible adaptation of cryptophytes in response to environmental stresses.
Source: Nature Communications
Authors: Long Si, Shumeng Zhang, Xiaodong Su, Mei Li
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $6,790
Funders: National Natural Science Foundation of China, Chinese Academy of Sciences, Youth Innovation Promotion Association of the Chinese Academy of Sciences, University of Chinese Academy of Sciences, Institute of Botany, Chinese Academy of Sciences, Youth Innovation Promotion Association, Institute of Biophysics, Chinese Academy of Sciences
OpenAlex ID: W4401463735