Partial degradation of the extrinsic 23-kDa protein of the Photosystem II complex of spinach |
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Authors: | Mitsue Miyao Yoko Fujimura Norio Murata |
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Institution: | National Institute for Basic Biology, Myodaiji, Okazaki, Japan |
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Abstract: | Chymotrypsin eliminated nine amino acid residues at the amino-terminal side of the extrinsic 23-kDa protein of the oxygen-evolving Photosystem II complex of spinach. The resultant 22-kDa fragment was able to bind to the Photosystem II complex but with lowered binding affinity. However, once the 22-kDa fragment bound to the complex, it retained most functions of the 23-kDa protein; the fragment provided a binding site for the extrinsic 18-kDa protein, preserved a tight trap for Ca2+ in the complex, and shifted the optimum Cl? concentration for oxygen evolution from 30 to 10 mM, although it was less effective in sustaining oxygen evolution at Cl? concentrations below 10 mM. These observations suggest that the elimination of nine amino acid residues at the amino-terminal region of the 23-kDa protein does not significantly alter the conformation of the protein, except for partial modification of its binding site and its interaction with Cl?. |
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Keywords: | Extrinsic 23 kDa protein Oxygen evolution Photosystem II Photosynthesis (Spinach) |
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