Ion transport across model lipid membranes containing light-harvesting complex II: an effect of light.
The effect of light on proton transport across lipid membranes of small unilamellar liposomes containing incorporated major light-harvesting pigment-protein complex of Photosystem II (LHCII) has been studied with the application of pH-sensitive dyes entrapped inside vesicles. Proton permeability coefficient for LHCII-modified membranes was found to be about twice as high as in the case of the control pure lipid vesicles. Illumination of the samples with light absorbed by the LHCII-bound photosynthetic pigments considerably affects the kinetics of proton transport: it increases the rate and decreases the steady-state level of proton gradient across the membranes. The effect was interpreted in terms of heat-induced conformational changes of LHCII molecular structures that affect proton buffering capacity of this protein. Both the control and the LHCII-modified lipid membranes have been found to be practically impermeable to Ca(++) ions, as demonstrated by fluorescence of liposome-entrapped calcium-sensitive probe calcium crimson. The slight differences in the proton transport across the LHCII-containing membranes under the presence of Ca(++) suggest calcium binding to this antenna protein.
Iwaszko
Ewa
E
Department of Biophysics, Institute of Physics, Maria Curie-Skłodowska University, PL. M. Curie-Sklodowskiej 1, Lublin 20-031, Poland.
Wardak
Anna
A
Krupa
Zbigniew
Z
Gruszecki
Wiesław I
WI
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism / Q000528:radiation effects; D002645:Chickens; D004530:Egg Yolk / Q000378:metabolism; D005456:Fluorescent Dyes / Q000494:pharmacology; D017136:Ion Transport / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D008081:Liposomes / Q000378:metabolism* / Q000528:radiation effects*; D009930:Organic Chemicals; D010637:Phenolsulfonphthalein / Q000031:analogs & derivatives* / Q000494:pharmacology; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D011522:Protons; D012434:Secale / Q000201:enzymology; D013050:Spectrometry, Fluorescence
D005456:Fluorescent Dyes; D008081:Liposomes; D009930:Organic Chemicals; D045332:Photosystem II Protein Complex; D011522:Protons; C071334:calcium crimson; C009743:Cresol red; D010637:Phenolsulfonphthalein; D002118:Calcium