Electric properties of thylakoid membranes from pea mutants with modified carotenoid and chlorophyll-protein complex composition

Surface electric properties of thylakoid membranes from wild type and two m utant forms, Coeruleovireus 2/16 and Costata 2/133, of pea are investigated by electric light scattering and microelectrophoretic measurements. Charac terization of the chlorophyll-protein complexes in thylakoid membranes reve als that the relative ratio of oligomeric (LHC II1) to monomeric (LHC II3) forms of the light-harvesting Chl a/b complex of Photosystem II is lower (3 .34) in 2/133 mutant and higher (6.62) in 2/16 mutant than in wild type (4. 57). This is accompanied by elevated amounts and a considerable reduction o f all carotenoids in 2/16 and 2/133 mutant, respectively, as compared to th e wild type. The concomitant variations of the permanent dipole moment (tra nsversal charge asymmetry), electric polarizability and electrokinetic char ge of the thylakoid membranes from both the mutants are discussed in terms of the differences in the supramolecular (oligomeric) organization of the l ight-harvesting complexes II within the photosynthetic apparatus.