期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1981
卷号：78
期号：12
页码：7507-7511
DOI：10.1073/pnas.78.12.7507
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Chloroplast thylakoid membranes isolated in the presence of EDTA retain high rates of O2 evolution ([≥]340 {micro}mol{middle dot}h-1{middle dot}mg chlorophyll-1) but contain no Mn2+ that is detectable by electron paramagnetic resonance (EPR) at room temperature. The total Mn2+ content of these preparations is 4.6 per 400 chlorophylls; 0.6 Mn2+ can be released by addition of Ca2+, a treatment that does not affect O2 evolution. The remaining Mn2+ (4 per 400 chlorophylls) appears to be functionally associated with O2 evolution activity. Inhibition by Tris, NH2OH, or heat will release a small fraction of Mn2+ from these membranes ({approx}25% with Tris, for example). Addition of Ca2+ further enhances Mn2+ release so that for Tris and for NH2OH, 2 and 3, respectively, Mn2+ per 400 chlorophylls are extracted from the O2-evolving complex. Based on the microwave power-saturation properties of the EPR signal IIf, which arises from an intermediate electron carrier in the water splitting process, it appears that one of the four Mn2+ associated with photosystem II is uniquely sensitive to Tris. A new model is proposed for the organization and inhibitor sensitivity of manganese in the O2-evolving complex.
关键词：photosynthesis ; electron paramagnetic resonance
