SURFACE ELECTRIC PROPERTIES OF THYLAKOID MEMBRANES FROM ARABIDOPSIS-THALIANA MUTANTS

Electric light scattering measurements of thylakoid membranes from wil d type and two mutant forms (JB67 and LK3) of Arabidopsis thaliana hav e shown that application of external electric pulses induces electric dipole moments of different origin. The asymmetric surface charge dist ribution and electric polarizability are significantly altered by the lipid modification. Mild trypsin treatment of Arabidopsis thylakoids l eading to digestion of small polypeptides from the light-harvesting ch lorophyll a/b protein complex of photosystem II (LHCP II) gives eviden ce for a lower content of LHCP II in the mutant forms. The results dem onstrate the significance of the level of thylakoid lipid unsaturation in determining the surface charge distribution through changes either in the pigment-protein content and membrane appression induced by the lipid modification or in the exposure of charged polypeptides on the thylakoid membrane surface(s) arising from alteration of the lipid geo metry. (C) 1997 Elsevier Science B.V.