(i) a first nucleic acid sequence that encodes a first seven-transmembrane receptor polypeptide that is the rhodopsin translocation peptide contained in SEQ ID NO:3 or a nucleic acid sequence encoding a variant of said rhodopsin translocation peptide, wherein said variant is identical to said rhodopsin translocation peptide but for a single conservative amino acid substitution which substitutes a first amino residue in a first group for a second amino acid residue within the first group, wherein the first group is selected from the groups consisting of: 1) Alanine (A), Serine (S), Threonine (T); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q); 4) Arginine (R), Lysine (K); 5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); and 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W); and

(ii) a second nucleic acid sequence that encodes a second seven-transmembrane receptor polypeptide, wherein said nucleic acid construct when expressed in a cell results in a hybrid seven-transmembrane receptor polypeptide comprising the rhodopsin translocation peptide or said variant, and the second seven-transmembrane receptor polypeptide, wherein the rhodopsin translocation peptide or said variant directs the translocation of the second seven-transmembrane receptor polypeptide across the cell membrane, wherein said variant translocates the seven-transmembrane receptor polypeptide as efficiently as the rhodopsin translocation polypeptide.