Localization of TGN38 to the trans-Golgi network: involvement of a cytoplasmic tyrosine-containing sequence

To further define the sequences responsible for TGN localization, an additional chimeric protein was constructed in which sequences encoding the lumenal and transmembrane domains of the Tac antigen were fused to sequences encoding the cytoplasmic domain of TGN38 (T-T-G, for Tac lumenal-Tac transmembrane-TGN38 cytoplasmic) (Fig. 1, top) . The T-T-G chimera was expressed by transient transfection of NRK cells, and its subcellular distribution studied by immunofluorescence microscopy. Like T-G-G, the T-T-G chimera was found to colocalize with endogenous TGN38 (Fig. 1 , e and f). Thus, a determinant sufficient for TGN localization was contained within the 33-amino acid cytoplasmic tall of TGN38.