Preparative isolation of adult human liver metallothionein isoforms

Preparative human liver metallothionein (MT) isolation is described. MT was saturated with cadmium to follow MT purification spectrophotometrically instead of by metal content and to increase the stability of the protein. A concentrated, MT-rich fraction of the liver cytosol was prepared by selective organic solvent (acetone or acetone/methanol) fractionation. Conventional gel filtration and ion-exchange chromatographies resolved two MT isoforms, MT-I and MT-II. When needed, purification of MT from other low-molecular weight proteins was further increased by gel filtration chromatography at zero ionic strength, i.e., in distilled water. Reversed-phase high performance liquid chromatography of both MT isoforms resolved further peaks sharing MT properties not only from the MT-I but also from the MT-II ion-exchange isoform. The results show that it is feasible to perform a human liver MT isolation from an entire human liver with a reasonable laboratory capability.