Evolution of oxygen-evolving PSII in view of the extrinsic proteins

点击翻译按钮获取中文摘要

Photosystem II (PSII) contains different extrinsic proteins among different organisms. Higher plant PSII contains the three extrinsic proteins of 33 kDa, 23 kDa and 17 kDa, whereas in cyanobacterial and red algal PSII, only the 33 kDa protein is present but the other two proteins are absent. Instead, two different proteins, cytochrome c550 and 12 kDa protein, were found in the latter organisms. In red algal PSII, a fourth extrinsic protein, a 20 kDa protein, was also found. These facts suggest that the oxygen-evolving complex changed the extrinsic proteins during its evolution from cyanobacteria to higher plants. This study aimed at elucidating the evolutionary process of oxygen-evolving PSII in terms of the changes of the extrinsic proteins. To reach this purpose, we planned to prepare the antibodies against the four extrinsic proteins of red algal PSII and to use them to detect the extrinsic proteins in various organisms. First, the genes encoding the four extrinsic proteins were cloned. Then, the cloned genes were successfully expressed in E.coli. and the antibodies against their recombinant proteins were prepared. We have collected various species of algal cells and are planning to examine the cross-reactivity of these algal cells against the antibodies we constructed, in order to clarify which organism contains which set of the extrinsic proteins.