The C-terminal region of TGBp3 contains the sorting determinant for forming puncta within cortical ER tubules. (A) GFP fused to the N-terminal (amino acids 1–30) and C-terminal (25–52) regions of TGBp3 expressed in yeast (SEY6210) for fluorescence microscopy. (B) Quantification scheme for various subcellular localizations shown in this study. N indicates the total number of cells counted. (C) Hybrid constructs as indicated were expressed in yeast cells and imaged by confocal microscopy (center) or coexpressed with Rtn1-mCherry (CWY2754) and imaged by fluorescence microscopy (periphery). (D) The indicated residues in TGBp3 were mutated from the GFP-p2^1-100-p3^25-52 construct. Yeast cells expressing these proteins were imaged by confocal microscopy. The bars on the bottom indicate quantification data. Bars, 5 µm.