Bovine adrenodoxin--a mitochondrial iron-sulphur protein--binds to chaperonin GroEL

The interaction of bovine adrenodoxin with the chaperonin GroEL was investigated using sucrose density centrifugation and analytical ultracentrifugation. It could be clearly established that denatured mature adrenodoxin comigrated in a sucrose density gradient with the GroEL oligomer, indicating that a complex had been formed. Up to 2 moles of adrenodoxin/mol GroEL can be bound. From the partial concentrations, association constants of 4.3 x 10(5) M-1 for the first adrenodoxin molecule and of 1.08 x 10(5) M-1 for the second molecule to the complex, respectively, were calculated. Upon addition of the cochaperonin GroES and Mg-ATP to the adrenodoxin-GroEL complex, adrenodoxin was released, indicating a specific binding between GroEL and adrenodoxin.