Abstract: Provided by this invention is a fusion protein which is capable of binding to Fas, and which comprises a peptide comprising at least a part of the amino acid sequence of Fas ligand, a peptide having oligomerization ability, and a peptide which increases recombinant protein production. Also provided are a method for using the FLAG-like peptide for the purpose of increasing the production of the recombinant protein, and a method for using the FLAG-like peptide for the purpose of increasing the biological activity of the fusion protein of the leucine zipper and the transmembrane protein.