Abstract: The present invention relates to an expression vector comprising, in 5? to 3? direction, a promoter, a multiple cloning site and a nucleotide sequence encoding glutathione-S-transferase (GST), for production of a fusion protein comprising a membrane protein, secretory protein or toxic protein or peptide, fused directly or indirectly with the N-terminal of GST. Preferably, the fusion protein comprises GST and a membrane protein or membrane localised peptide. The invention is especially suitable for membrane proteins having their C-terminals in the cytoplasm. The invention also relates to methods for producing such fusion proteins using host cells transformed with the expression vector in which a desired gene has been cloned.