Abstract
A two-step PCR method was taken to replace the cysteines at position 19, 29 in p domain of Metallothionein with histidines. Then the His19·29-mutant fragment was cloned into the vector pGEX-4T-l and expressed as a fusion protein of glutathione-S-transferase. After cleaved with thrombin and purified, the p domain with the substitution of Cys-to-His was obtained and identified by amino acid composition and molecular weight. The His19·29 mutant can bind with the same amount of zinc or cadmium ions as the p domain but exhibits stronger zinc binding ability and weaker cadmium binding ability.