the coppercontaining medium was exchanged to Talon buffer (50 mM phosphate buffer, pH 8.0, 300 mM NaCl) by Amicon (30-kDa cutoff membrane). The 10-fold concentrated sample (15 ml) in Talon buffer was then purified by immobilized metal affinity chromatography (IMAC). The sample was first adjusted to pH 8.0 by NaOH and then filtered (0.22 lm Acrodisc Gelman) prior to loading on a Fast flow column (Clontech) containing a 2 ml bed volume of Talon™ metal affinity resin (Clontech, Mountain View, CA). The support was first equilibrated with 20 ml of Talon buffer. After binding at 4 C for 30 min, the resin was washed with 20 ml of Talon buffer under gravity feed and the bound proteins were eluted by increasing the concentration of imidazole up to 200 mM in the Talon buffer.