Localization of ferredoxin in the thylakoid membrane with immunological methods.

Antibodies were prepared against ferredoxin isolated from spinach. These antibodies and those against TPN-ferredoxin-reductase, carboxydismutase and coupling factor were used to clarify the localization of these proteins in the thylakoid membrane. Chloroplast preparations obtained by different methods show not the same immunological reactions. Only lamellar systems suspended in the leaf homogenate are agglutinated by anti-ferredoxin. Washed lamellar systems show an agglutination with anti-ferredoxin only if ferredoxin is added. In certain preparations of lamellar systems the presence of ferredoxin inhibit the reaction of anti-TPN-ferredoxin-reductase with the lamellar system. Lamellar systems freed of coupling factor by EDTA treatment are agglutinated by anti-TPN-ferredoxin-reductase. Addition of coupling factor to the EDTA treated lamellar systems inhibit the agglutination but not the adsorption of TPN-ferredoxin-reductase antibodies. By the assumption that the inhibition of the agglutination by the TPN-ferredoxin-reductase antibodies is caused by sterical hindrance, these results indicate, that ferredoxin, coupling factor and TPN-ferredoxin-reductase are localized close to each other in the thylakoid membrane. Lamellar systems suspended in leaf homogenate are agglutinated by anti-TPN-ferredoxinreductase. That means, that to a certain extend the molecular structure of the thylakoid membrane changes with the kind of preparations employed.