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Plant Physiology 82:499-502 (1986) © 1986 American Society of Plant Biologists Localization and Quantitative Determination of Ferredoxin-NADP+ Oxidoreductase, a Thylakoid-Bound Enzyme in the Cyanobacterium Anabaena sp. Strain 7119 1,2Centro de Estudios Fotosintéticos y Bioquímicos, Consejo Nacional de Investigaciones Científicas y Técnicas, Fundación Miguel Lillo, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
Thylakoid membrane preparations obtained from mechanically disrupted (sonicated) cells of the cyanobacterium Anabaena sp. strain 7119 show a membrane-bound ferredoxin-NADP+ oxidoreductase (EC 1.18.1.2) as determined either by specific antibodies or by using the ferredoxin-dependent NADPH-cytochrome c reductase activity, which is a specific test for this enzyme. However, in contrast with higher plant thylakoids, a low yield of the cyanobacterial reductaseonly about 20% of the total amount of this protein estimated in whole cell homogenateswas obtained as a membrane-bound form when Mg2+ was present during the disruption treatment. It is noteworthy that the addition of water-soluble nonionic polymers, namely polyethylene glycol and polyyinylpyrrolidone, dramatically increased the yield of the thylakoid-bound reductase, reaching values up to 80 to 85% of the total enzyme. Using these thylakoid membrane preparations, a quantitative determination of the reductase has been performed for the first time for cyanobacterial thylakoids. The value determined by immunoelectrophoresisfrom 8 to 10 nanomoles per micromole of chlorophyllis clearly higher than those reported for chloroplast thylakoids.
3 Permanent address: Depto. de Bioquímica, Fac. de Biología y C.S.I.C., Univ. de Sevilla, Apdo. 1095, 41080-Sevilla, Spain. 1 Supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina), R. H. V. is a member of the Investigator Career and A. S. a Fellow of the same Institution. 2 Dedicated to Dr. Luis F. Leloir on the occasion of his 80th birthday, September 6, 1986.
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