Thermostability and Ca2+ Binding Properties of Wild Type and Heterologously Expressed PsbO Protein from Cyanobacterial Photosystem II

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• 作者：Bernhard Loll ; Gisa Gerold ; Daria Slowik ; Wolfgang Voelter ; Christiane Jung ; Wolfram Saenger ; and Klaus-Dieter Irrgang
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：March 29, 2005
• 年：2005
• 卷：44
• 期：12
• 页码：4691 - 4698
• 全文大小：115K
• 年卷期：v.44,no.12(March 29, 2005)
• ISSN：1520-4995

文摘

Oxygenic photosynthesis takes place in the thylakoid membrane of cyanobacteria, algae, andhigher plants. Initially light is absorbed by an oligomeric pigment-protein complex designated asphotosystem II (PSII), which catalyzes light-induced water cleavage under release of molecular oxygenfor the biosphere on our planet. The membrane-extrinsic manganese stabilizing protein (PsbO) is associatedon the lumenal side of the thylakoids close to the redox-active (Mn)₄Ca cluster at the catalytically activesite of PSII. Recombinant PsbO from the thermophilic cyanobacterium Thermosynechococcus elongatuswas expressed in Escherichia coli and spectroscopically characterized. The secondary structure ofrecombinant PsbO (recPsbO) was analyzed in the absence and presence of Ca²⁺ using Fourier transforminfrared spectroscopy (FTIR) and circular dichroism spectropolarimetry (CD). No significant structuralchanges could be observed when the PSII subunit was titrated with Ca²⁺ in vitro. These findings arecompared with data for spinach PsbO. Our results are discussed in the light of the recent 3D-structuralanalysis of the oxygen-evolving PSII and structural/thermodynamic differences between the two homologousproteins from thermophilic cyanobacteria and plants.