CHANGES IN THE LOCALIZATION OF THE PROTEINS IN ISOLATED INNER MEMBRANES FROM WHEAT ETIOCHLOROPLASTS UNDER IRRADIATION, MEASURED BY 1-ANILLINO-8-NAPHTHALENE SULFONATE AND PYRENE

Reformed prolamellar bodies and thylakoids were isolated from dark gro wn wheat leaves irradiated with white light (4.4 Wm(-2)) for 4 h and r edarkened for 16 h. The isolated membranes were irradiated with brief saturating light: and transferred back to darkness. The changes of roo m-temperature fluorescence of the tryptophan residues from the membran e proteins in presence and in absence of the fluorescence probes 1-ani lino-8-naphthalene sulfonate (ANS) and pyrene were investigated. The a im was to study the light-induced changes in the conformation of membr ane proteins and their membrane localisation. Simultaneously, the chan ges in low temperature fluorescence spectra of the pigments were also registered. The accessibility of the tryptophan residues in reformed p rolamellar bodies and thylakiod membranes before and after irradiation showed that most of their membrane proteins were localised on the sur face of the lipid phase or slightly penetrated it. This was better sho wn for the thylakoid membranes, probably because of their planar struc ture. The registered alterations of the efficiency of energy transfer from tryptophan to the fluorescence probes after irradiation could be explained by accepting the idea that in nonirradiated prolamellar bodi es, NADPH-protochlorophyllide oxidoreductase (POR)-Protochlorophyllide -NADPH complexes are arranged in large aggregates that start to separa te to smaller complexes after irradiation. This supports the hypothesi s that the irradiation of PLB membranes causes a lateral diffusion of NADPH-protochlorophyllide oxidoreductase dissociates on the membrane s urface.