Purification of a metallothionein-like protein from serum of mercury-treated rats using phosphorylcholine-Sepharose...

A metallothionein-like protein (MLP) from the serum of mercury-treated rats was isolated while purifying an acute phase plasma protein, C-reactive protein, by its Ca2(+)-dependent affinity to phosphorylcholine (PC)-Sepharose column. The MLP was further purified by a single DEAE-Sephacel ion-exchange chromatography. The MLP is similar to mammalian hepatic Zn-metallothionein on the basis of its low molecular weight of approximately 7000, 7 g Zn atoms/molecule of MLP and an absorption maximum at 220 nm. The purity of the protein was confirmed by double immunodiffusion test against anti-MLP antiserum raised in a rabbit. Immunologically MLP was detected not only in the hepatic cytosol, serum and urine from Hg-treated rats but also in the serum and hepatic cytosol of untreated rats. Using PC-Sepharose column, MLP could not be purified from normal serum.