Golgin 45, also known as JEM-1 or basic leucine-zipper nuclear factor 1, is a 400 amino acid protein that localizes to the lumen of the Golgi apparatus. The primary function of golgin 45 is to maintain normal Golgi structure and to facilitate protein transport from the endoplasmic reticulum to the cell surface. The latter process is regulated primarily through the interaction of golgin 45 and GRASP55, which together form a Rab 2 effector complex. Excluding formation of a Rab 2 complex, golgin 45 does not interact with any other Golgi Rab proteins. Golgin 45 is expressed as two isoforms, one of which localizes to the nucleus and is thought to function as a transcription factor.