Crystallization of a covalently-linked complex of adrenodoxin and adrenodoxin reductase

Two forms of mitochondrial adrenodoxin reductase from bovine adrenals and recombinant bovine adrenodoxin and adrenodoxin reductase expressed in Escherichia coli were isolated, purified to homogeneity and biochemically characterized. Recombinant adrenodoxin reductase was expressed as a single polypeptide; its retention time on DEAE-Fractogel coincides with the second form (F2) of the mitochondrial reductase. Two enzyme forms have similar adrenodoxin reductase activities in two types of systems comprising either cytochrome c or cytochrome P-450 (11 beta) as the terminal electron acceptor. Adrenodoxin and each of two reductase forms were cross-linked using 1-ethyl-3-(dimethyl-amino-propyl)carbodiimide. An effective two-step method for the purification of the active heterologous cross-linked complexes is suggested that enables purification of the functional complexes to homogeneity. The cross-linked bimolecular complex of adrenodoxin and adrenodoxin reductase was crystallized for the first time.