A new procedure for fast isolation and purification of plastocyanin from the cyanobacterium Anabaena variabilis.

Methods are described for growing the cyanobacterium A. variabilis and for the isolation and purification of plastocyanin from the grown culture. Cell paste which had been stored at -35°C was suspended in 1 mM MES buffer, pH 6.5 and centrifuged. The supernatant was diluted to a conductivity of 0.12 mS, [Fe(CN)6](3-) added to a concentration of 0.5 mM and the solution loaded on a S Sepharose Fast Flow column. After elution and ultrafiltration, the plastocyanin containing fractions were reloaded on a S Sepharose Fast Flow column for final purification. A typical yield in three days from cells harvested from 3×20 l of medium was 32 mg plastocyanin with a minimum absorbance ratio A278/A597=1.14. This procedure is faster and the yield higher than for previous procedures.