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1.
2.
A cytochrome b
6
f deficient mutant of Lemna perpusilla maintains a constant and lower level of the light-harvesting chl a/b-binding protein complex II (LHC II) as compared to the wild type plants at low-light intensities. Inhibition of the plastoquinone
pool reduction increases the LHC II content of the mutant at both low- and high-light intensities but only at high-light intensity
in the wild type plants. Proteolytic activity against LHC II appears during high-light photoacclimation of wild type plants.
However, the acclimative protease is present in the mutant at both light intensities. These and additional results suggest
that the plastoquinone redox state serves as the major signal-transducing component in the photoacclimation process affecting
both, synthesis and degradation of LHC II and appearance of acclimative LHC II proteolysis. The plastoquinol pool cannot be
oxidized by linear electron flow in the mutant plants which are locked in a ‘high light’ acclimation state. The cytochrome
b
6
f complex may be involved indirectly in the regulation of photoacclimation via 1) regulation of the plastoquinone redox state;
2) regulation of the redox-controlled thylakoid protein kinase allowing exposure of the dephosphorylated LHC II to acclimative
proteolysis.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
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. 相似文献