Chen, C.L., Shim, M.S., Chung, J., Yoo, H.S., Ha, J.M., Kim, J.Y., Choi, J., Zang, S.L., Hou, X., Carlson, B.A., Hatfield, D.L., Lee, B.J. (2006). G-rich, a Drosophila selenoprotein, is a Golgi-resident type III membrane protein.  Biochem. Biophys. Res. Commun. 348(4): 1296--1301.

FBrf0192392

Research paper

G-rich is a Drosophila melanogaster selenoprotein, which is a homologue of human and mouse SelK. Subcellular localization analysis using GFP-tagged G-rich showed that G-rich was localized in the Golgi apparatus. The fusion protein was co-localized with the Golgi marker proteins but not with an endoplasmic reticulum (ER) marker protein in Drosophila SL2 cells. Bioinformatic analysis of G-rich suggests that this protein is either type II or type III transmembrane protein. To determine the type of transmembrane protein experimentally, GFP-G-rich in which GFP was tagged at the N-terminus of G-rich, or G-rich-GFP in which GFP was tagged at the C-terminus of G-rich, were expressed in SL2 cells. The tagged proteins were then digested with trypsin, and analyzed by Western blot analysis. The results showed that the C-terminus of the G-rich protein was exposed to the cytoplasm indicating it is a type III microsomal membrane protein. G-rich is the first selenoprotein identified in the Golgi apparatus.