Association of ferredoxin‐NADP⁺ oxidoreductase with the chloroplast cytochrome b‐f complex

The 37‐kDa non‐heme component in spinach cytochrome b‐f complex prepared from EDTA‐washed thylakoids [(1983) J. Biol. Chem. 258, 10348‐10354] is shown to be ferredoxin‐NADP + oxidoreductase (EC 1.18.1.2) on the basis of immunoreactivity, amino acid analysis, and pattern of cleavage by cyanogen bromide. Strong binding of the reductase to the isolated cytochrome complex suggests this is an important site for its attachment to the thylakoid membrane in vivo.