Binding of isolated proteins to Zn²⁺. After metal-ion affinity columns were charged with excess Zn²⁺or buffer alone, VN, uPAR, or single-chain urokinase type plasminogen activator (ScuPA), respectively, were allowed to bind to the column. Subsequent elution was performed with either binding buffer alone (lanes 1, 3, 5) or containing 0.05 mol/L EDTA (lanes 2, 4, 6). VN, uPAR, or ScuPA bound to the Zn²⁺ charged column, but not to a control column (not shown). The respective authentic protein bands are indicated by arrows on the right (monomeric and dimeric VN).