TY - JOUR
T1 - Involvement of the light-harvesting complex in cation regulation of excitation energy distribution in chloroplasts
AU - Burke, J. J.
AU - Ditto, C. L.
AU - Arntzen, C. J.
N1 - Funding Information:
1 Supported in part by DOE Contract No. EE-77-S-02-4475. A006 2 Mention of a trademark name or a proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture or the University of Illinois and does not imply approval of the product to the exclusion of others that may also be suitable.
Funding Information:
3 NIH predoctoral trainee (NIH Grant No. 6M7283-1).
PY - 1978/4/15
Y1 - 1978/4/15
N2 - A highly purified light-harvesting pigment-protein complex (LHC) was obtained by fractionation of cation-depleted chloroplast membranes using the nonionic detergent, Triton X-100. The isolated LHC had a chlorophyll a b ratio of 1.2 and exhibited no photochemical activity. SDS-polyacrylamide gel electrophoresis of the LHC revealed three polypeptides in the molecular weight classes of 23, 25, and 30 × 103. Antibodies were prepared against the LHC and their specificity was established. The effect of the α-LHC (antibodies to LHC) on salt-mediated changes in PS I and PS II photochemistry, Chl α fluorescence inductions, and 77 °K fluorescence emission spectra was investigated. The results show that: (i) The Mg2+-induced 20% decrease in photosystem I (PS I) quantum yield observed in control chloroplasts was blocked by the presence of the α-LHC antibody, (ii) The Mg2+-induced 70% increase in photosystem II (PS II) quantum yield of control chloroplasts was reduced 35% for plastids in the presence of α-LHC antibody, (iii) The Mg2+-induced increase in room-temperature variable fluorescence was reduced 60% by α-LHC antibody, (iv) The Mg2+-induced increase in the F685 F730 emission peak ratio at 77 °K was inhibited 50% in the presence of α-LHC antibody. These results provide direct evidence for the involvement of the light-harvesting complex in cation regulation of energy redistribution between the photosystems. The fact that the α-LHC antibody does not fully block Mg2+-induced PS II increases or chlorophyll fluorescence increases supports the concept that Mg2+ has two mechanisms of action: one effect on energy distribution and a second direct effect on photosystem II centers.
AB - A highly purified light-harvesting pigment-protein complex (LHC) was obtained by fractionation of cation-depleted chloroplast membranes using the nonionic detergent, Triton X-100. The isolated LHC had a chlorophyll a b ratio of 1.2 and exhibited no photochemical activity. SDS-polyacrylamide gel electrophoresis of the LHC revealed three polypeptides in the molecular weight classes of 23, 25, and 30 × 103. Antibodies were prepared against the LHC and their specificity was established. The effect of the α-LHC (antibodies to LHC) on salt-mediated changes in PS I and PS II photochemistry, Chl α fluorescence inductions, and 77 °K fluorescence emission spectra was investigated. The results show that: (i) The Mg2+-induced 20% decrease in photosystem I (PS I) quantum yield observed in control chloroplasts was blocked by the presence of the α-LHC antibody, (ii) The Mg2+-induced 70% increase in photosystem II (PS II) quantum yield of control chloroplasts was reduced 35% for plastids in the presence of α-LHC antibody, (iii) The Mg2+-induced increase in room-temperature variable fluorescence was reduced 60% by α-LHC antibody, (iv) The Mg2+-induced increase in the F685 F730 emission peak ratio at 77 °K was inhibited 50% in the presence of α-LHC antibody. These results provide direct evidence for the involvement of the light-harvesting complex in cation regulation of energy redistribution between the photosystems. The fact that the α-LHC antibody does not fully block Mg2+-induced PS II increases or chlorophyll fluorescence increases supports the concept that Mg2+ has two mechanisms of action: one effect on energy distribution and a second direct effect on photosystem II centers.
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U2 - 10.1016/0003-9861(78)90031-0
DO - 10.1016/0003-9861(78)90031-0
M3 - Article
C2 - 655723
AN - SCOPUS:0017821156
SN - 0003-9861
VL - 187
SP - 252
EP - 263
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 1
ER -