The sweet protein monellin gene was expressed in Saccharomyces cerevisiae under the control of the GAL1 promoter and alpha-factor signal peptide sequence of S. cerevisiae. The gene, which was obtained through mutation of the synthesized single-chain monellin gene, was cloned into an E. coli-yeast shuttle vector pYES2.0 which carries the galactose-inducible promoter GAL1. Then the alpha-factor signal peptide of S. cerevisiae was linked also, resulting in the secreting expression vector pYESMTA. The recombinant plasmid was subsequently transformed into strain S. cerevisiae INVsc1. The peptide efficiently directed the secretion of monellin from the recombinant yeast cell. A maximum yield of active monellin was 0.41 g l(-1) of the supernatant from INVsc1 harboring pYESMTA.