Regulation of Photosystem II core protein phosphorylation at the substrate level: Light induces exposure of the CP43 chlorophyll a protein complex to thylakoid protein kinase(s) |
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Authors: | Vink Martin Zer Hagit Herrmann Reinhold G Andersson Bertil Ohad Itzhak |
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Institution: | Department of Biochemistry, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, S-106 91, Sweden. |
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Abstract: | Light induces conformational changes in the CP43 chl-a-protein antenna complex in isolated PS II core-complexes exposing phosphorylation site(s) to PS II core-associated protein
kinase(s), to added solubilized thylakoid protein kinase(s), as well as to tryptic cleavage. The substrate-activation effect
is demonstrated by exposure of the PS II cores to light during the kinase assay as well as by preillumination of the PS II
cores in which the endogenous kinase(s) has been inactivated by treatment with N-ethylmaleimid. In the latter case, phosphorylation
was performed in darkness following addition of the solubilized protein kinase(s). The solubilized protein kinase(s) does
not require light activation. The apparent molecular masses of the main protein kinase(s) associated with the PS II cores
(about 31–35 kDa and 45 kDa) differ from that of the major protein kinase present in solubilized preparations obtained from
spinach thylakoids (64 kDa). The light-induced exposure of CP43 increases with the light intensity in the range of 20–100
μmol photons m−2 s−1 as demonstrated by preillumination of N-ethylmaleimid treated cores followed by addition of the solubilized protein kinase(s)
and performing the phosphorylation assay in darkness.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | conformational changes CP43 complex D1 protein protein kinase protein phosphorylation phosphothreonine antibodies PS II cores trypsin cleavage |
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