Isolation and properties of plastocyanin from Anabaena variabilis

Plastocyanin is a copper protein found in photosynethetic tissue and it exhibits the properties of a physiological redox reagent. This protein has been purified from the blue-green alga Anabaena variabilis. Plastocyanin is required for a number of partial reactions of the photosynthetic electron transfer chain. These reactions include the transfer of electrons from reduced 2,3′,6-trichlorophenolindophenol,N,N,N′,N′- tetramethyl-p-phenylenediamine and 2,3,5,6-tetramethyl-p-phenylenediamine to low potential oxidants. Reduced cytochrome c photooxidation does not appear to be dependent on plastocyanin. Cytochrome f, isolated from this alga, will partially replace plastocyanin in many of these reations. Inhibition of photosynthetic reactions by copper chelators appears to occur at some site other than the site of plastocyanin function.