Separation of cobalt binding proteins by immobilized metal affinity chromatography

Cobalt binding proteins from mouse liver, which were expressed in response to CoCl2 poisoning, were separated using gel permeation chromatography and then immobilised metal ion affinity chromatography (IMAC) with immobilized cobalt ions. Conditions used in IMAC-Co2+ were optimised. The fractions eluted with 60 mM imidazole were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE). Differences between the samples were also evaluated by a two-dimensional electrophoresis. Samples from the Co2+-treated mice provided higher number of electrophoretic spots than those from the untreated mice. Relative molecular masses of these proteins are appropriately 37,000; 32,000 and 26,000 and their isoelectric points (pI) are 6.5–7.5.