Isolation and Partial Characterization of Ferredoxin from Zea mays

Ferredoxins have been isolated and purified from several varieties of higher plants. These proteins appear to have similar molecular weights (10-12,000), contain 2 g-atoms of iron per mole, and support photoreduction of NADP with chloroplasts. Recently, great interest has been focused on some plant species that have a high photosynthetic capacity for CO, assimilation. These include many of the tropical grasses such as corn, sugar cane, and sorghum. With these species, CO, appears to be fixed by a pathway in which C-dicarboxylic acids (oxalacetate, malate, and aspartate) are the initial primary products (2, 3). However, most of the ferredoxins which have been studied are confined to those plants having a lower photosynthetic capacity where 3-phosphoglycerate is the initial product of CO fixation (C, pathway). Since the carbon products of photosynthesis differed, we thought it possible that the ferredoxins involved in photoreduction of NADP from the two plant types might differ. A technique for isolation and purification of ferredoxin in good yields from leaves of Zea mays has been developed and the amino acid composition, molecular weight, and biological activity of the protein have been determined.