The conventional translation initiator sequence for heterologous expression of metallothionein III (MTIII) in Saccharomyces cerevisiae was replaced by a yeast consensus initiator region (CAAAAUG). Saccharomyces cerevisiae was transformed with a vector carrying the MTIII gene and the modified initiator sequence had a much higher metal tolerance, Cd accumulation and MTIII production than that with the original initiator sequence, although the level of gene transcripts was similar in both systems. This modification markedly improves MTIII production and may also be used for production of other genes.