Physical map of giantin cDNA fragments used in epitope analysis. The open box denotes the open reading frame. P1–P6 represent overlapping segments expressed as recombinant proteins, together spanning almost the full length of giantin. The P1 fragment differs from the published sequence and represents an alternatively mRNA spliced product. (b) Coiled-coil domains of giantin, golgin-245, golgin-160, golgin-95/GM130, and golgin-97. Each macromolecule is depicted showing the coiled-coil regions, as predicted by the COILS program . A transmembrane (TM) hydrophobic region of 20–22 amino acids at the carboxyl-terminus is postulated to be responsible for anchoring giantin to Golgi membrane, with the molecule extending to the cytoplasm. The cytoplasmic domains of giantin are responsible for interaction with other Golgi proteins GM130 and p115.