The oxygen-evolving centre of Photosystem II (PS II) is located on the lumenal side of the PS II complex and is surrounded by a group of polypeptides known as the extrinsic proteins. In PS II of the cyanobacterium Synechocystis sp. PCC 6803 six extrinsic proteins have been identified: PsbO, PsbP, PsbQ, PsbU, PsbV and Psb27. We have obtained two X-ray crystallographic structures of PsbQ, from crystals grown in either the presence or absence of Zn2+ ions. The structures were solved by multiple wavelength anomalous dispersion phasing using data obtained from a selenomethionine derivative and have essentially identical structures. The protein was found to consist of a four-helix bundle with an up-down-up-down fold. His76 (present in a unique HisGlyPro motif which forms a kink in helix 2 of cyanobacterial PsbQ) together with Asp116 (helix 3), coordinates Zn adjacent to a hydrophobic cavity on the H2/H3 face. We hypothesize this metal binding site and cavity may play a role in a protein-protein interaction with another PS II subunit. Similar structure-function studies are underway for the PsbP subunit; to facilitate solving the structure of PsbP in solution we have determined the NMR backbone chemical shift values of isotopically labelled recombinant PsbP.
CITATION STYLE
Jackson, S. A., Fagerlund, R. D., Hinds, M. G., Wilbanks, S. M., & Eaton-Rye, J. J. (2013). Structure-function studies of the photosystem II extrinsic subunits PsbQ and PsbP from the cyanobacterium synechocystis sp. PCC 6803. In Advanced Topics in Science and Technology in China (pp. 86–90). Springer Science and Business Media Deutschland GmbH. https://doi.org/10.1007/978-3-642-32034-7_19
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