Four Ferredoxins from Japanese Radish Leaves

We detected three ferredoxin components, a, b, and c, in green shoots of Japanese radish seedlings by hydrophobic HPLC analysis using a phenyl-5PW column. All components were also present in mature leaves. Component a was further separated into two components, a1 and a2, by reversed-phase HPLC after carboxymethylation. The existence of four ferredoxins in the photosynthetic tissue of a single plant species is reported here for the first time. Each individual ferredoxin component was isolated, and its primary structure was analyzed for comparison with the two leaf ferredoxins, L-Fds A and B, isolated by Wada et al. (J. Biochem. 105, 619-625 (1989)). The primary structures of components a1, a2, and b were all found in 12 possible structures of L-Fd A deducible from its microheterogeneities. This led us to conclude that L-Fd A is a mixture of three ferredoxins corresponding to components a1, a2, and b. The complete primary structure of component c was established by sequencing of the whole protein and of peptides generated by protease digestion. The N-terminal structure of component c was identical with L-Fd B up to the 11th amino acid residue, suggesting that this component is the same ferredoxin as L-Fd B.