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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 31, Number 6
BKCSDE 31(6)
June 20, 2010 

Expression and pH-dependence of the Photosystem II Subunit S from Arabidopsis thaliana
Mi Suk Jeong, Eun Young Hwang, Gyoung Ean Jin, So Young Park, Ismayil S Zulfugarov, Yong Hwan Moon, Choon Hwan Lee, Se Bok Jang*
Photosystem II subunit S, Expression, pH dependence, Temperature dependence
Photosynthesis uses light energy to drive the oxidation of water at an oxygen-evolving catalytic site within photosystem II (PSII). Chlorophyll binding by the photosystem II subunit S protein, PsbS, was found to be necessary for energy-dependent quenching (qE), the major energy-dependent component of non-photochemical quenching (NPQ) in Arabidopsis thaliana. It is proposed that PsbS acts as a trigger of the conformational change that leads to the establishment of nonphotochemical quenching. However, the exact structure and function of PsbS in PSII are still unknown. Here, we clone and express the recombinant PsbS gene from Arabidopsis thaliana in E. coli and purify the resulting homogeneous protein. We used various biochemical and biophysical techniques to elucidate PsbS structure and function, including circular dichroism (CD), fluorescence, and DSC. The protein shows optimal stability at 4 oC and pH 7.5. The CD spectra of PsbS show that the conformational changes of the protein were strongly dependent on pH conditions. The CD curve for PsbS at pH 10.5 curve had the deepest negative peak and the peak of PsbS at pH 4.5 was the least negative. The fluorescence emission spectrum of the purified PsbS protein was also measured, and the λmax was found to be at 328 nm. PsbS revealed some structural changes under varying temperature and oxygen gas condition.
1479 - 1484
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