DETERMINATION OF GLYCOLIPIDS, SULFOLIPID AND PHOSPHOLIPIDS IN THE THYLAKOID MEMBRANE

Determination of binding of antibodies to lipids onto the surface of t he thylakoid membrane, before and after the removal of the CF1-complex with sodium bromide, showed that in the immediate vicinity of CF1 sul folipid and monogalactolipid occur in higher concentration and are the refore arranged in domains. The molar ratio of the CF1-complex to glyc olipids was determined in Nicotiana tabacum chloroplasts of different structure. Thus, in the chlorophyll-deficient tobacco mutants N. tabac um Su/su and Su/su var. Aurea, the molar ratio of CF1/monogalactolipid is the same and found to be 1:570. The structure of the lamellar syst em in these mutants is characterized by a higher ratio of stroma lamel lae to grana stacks when compared to the green wild type. In the wild type the ratio CF1/monogalactolipid is 30 per cent larger (1:740). In contrast to this the molar ratio CF1/sulfolipid and CF1/digalactolipid is the same in the wild type and the Su/su mutant, whereas these rati os are twice as high in the yellow mutant Nicotiana tabacum Su/su var. Aurea. The binding of glycolipids and phospholipids onto the subunits of CF1 from Spinacia oleracea was determined in the Western blot proc edure by using monospecific antisera. These experiments lead to the re sult that the two large subunits (alpha and beta) are marked by antise ra to monogalactosyldiglyceride, digalactosyldiglyceride and sulfoquin ovosyldiglyceride. The antisera to phospholipids react differently: wh ereas the antiserum to phosphatidylinositol only reacts with the alpha -subunit, the antiserum to phosphatidylcholine and that to phosphatidy lglycerol react just as the antisera to glycolipids with both large su bunits. It is observed that the antiserum to monogalactolipid occasion ally marks the gamma-subunit. This might mean that the glycolipids and the respective phospholipids are tightly bound onto the reacting alph a- and beta-subunits of the CF1-complex. Incubation of the subunit CF1 with lipase from Rhizopus arrhizus and with phospholipase C from Chlo stridium perfringens after their transfer to the nitrocellulose membra ne abolishes the positive reaction of the peptides with the antisera t o glycolipids and phospholipids.