We claim an isolated nucleic acid molecule encoding a ligand binding domain of glucose regulated protein of 94 kDa (GRP94), a chimeric polynucleotide consisting of said nucleic acid molecule operably linked to a heterologous promoter wherein said nucleic acid molecule is optionally linked to a polynucleotide encoding a heterologous polypeptide so as to form a fusion protein between the GRP94 ligand binding domain polypeptide and said heterologous polypeptide, a vector consisting of said chimeric polynucleotide, and a host cell comprising said chimeric polynucleotide.