The second ferredoxin from spinach leaves.

A minor component of ferredoxin (about 20% of the total content) was separated from the major one on a DEAE Trisacryl M column only after carboxymethylation of the ferredoxin purified from spinach leaves by the conventional procedure. The amino acid compositions and terminal sequences of the two revealed that the major component corresponded to the one previously sequenced (Matsubara, H. & Sasaki, M. (1968) J. Biol. Chem. 243, 1732-1757) and the minor one had a completely different structure from that of the major one. Comparison of the amino(N)-terminal 34 residues showed 11 amino acid substitutions between the two components. Thus the existence of a second ferredoxin was demonstrated in spinach leaves.