Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 286, Issue 34, Pages 29548-29555Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M111.238394
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Funding
- Deutsche Forschungsgemeinschaft [SFB 480, C1]
- Protein Research Department of the Ruhr-Universitat Bochum
- European Union
- Swedish Research Council
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The multisubunit membrane protein complex Photosystem II (PSII) catalyzes one of the key reactions in photosynthesis: the light-driven oxidation of water. Here, we focus on the role of the Psb27 assembly factor, which is involved in biogenesis and repair after light-induced damage of the complex. Weshow that Psb27 is essential for the survival of cyanobacterial cells grown under stress conditions. The combination of cold stress (30 degrees C) and high light stress (1000 mu mol of photons x m(-2) x s(-1)) led to complete inhibition of growth in a Delta psb27 mutant strain of the thermophilic cyanobacterium Thermosynechococcus elongatus, whereas wild-type cells continued to grow. Moreover, Psb27-containing PSII complexes became the predominant PSII species in preparations from wild-type cells grown under cold stress. Two different PSII-Psb27 complexes were isolated and characterized in this study. The first complex represents the known monomeric PSII-Psb27 species, which is involved in the assembly of PSII. Additionally, a novel dimeric PSII-Psb27 complex could be allocated in the repair cycle, i.e. in processes after inactivation of PSII, by N-15 pulse-label experiments followed by mass spectrometry analysis. Comparison with the corresponding PSII species from Delta psb27 mutant cells showed that Psb27 prevented the release of manganese from the previously inactivated complex. These results indicate a more complex role of the Psb27 protein within the life cycle of PSII, especially under stress conditions.
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