Untersuchungen über die Oberflächenstruktur des Thylokoidsystems der Chloroplasten mit Hilfe von Antikörpern gegen die Ferredoxin-NADP-Reduktase

Our earlier results are confirmed by new experiments with ultrasonically disrupted isolated thylakoid systems and with “broken chloroplasts”: Chloroplast membrane systems are not agglutinated directly by antisera against ferredoxin-NADP reductase, although this protein is an integral part of the surface of the thylakoids. An indirect agglutination of the preparations, however, occurs, when the thylakoid systems are incubated with antisera against the reductase and then an antiserum against rabbit-γ-globulin or soluble reductase is added. Therefore the hypothetical deepenings discussed in the former publication must be located in the surface of the outer membranes of the thylakoid stacks. The thylakoid systems cannot be agglutinated directly by antibodies against reductase, because the antibody molecules are too short to connect the reductase located in the deepenings of the particles. The minimum depth of the cavities therefore must be about 60 A. The maximum depth is estimated experimentally to be about 200 A. By treatment with EDTA the molecular structure of the thylakoid surface is altered in such a manner, that after this treatment the thylakoid systems can be agglutinated by antibodies against reductase directly. This treatment with EDTA is said to detach protruding knobs of the coupling factor of the photosynthetic phosphorylation. Thus our results are in agreement with the hypothesis, that the coupling factor is a protruding knob. Ferredoxin-NADP reductase would be located in the surface of the outer membranes of the thylakoid system between the knobs. - Other possible hypotheses to explain our immunological results are excluded by several control experiments.