Nicalin (NCLN)

The deduced type I transmembrane protein has a calculated molecular mass of 63.7 kD. Nicalin contains a region similar to an aminopeptidase domain, but it lacks amino acids necessary for catalytic activity. Northern blot analysis detected nicalin transcripts of 4.6, 4.0, and 2.3 kb. Highest expression was in pancreas and skeletal muscle, with somewhat lower expression in heart and very low expression in all other tissues examined. SDS-PAGE of enriched membrane preparations of human embryonic kidney cells and neuroblastoma cells indicated that endogenous nicalin has an apparent molecular mass of 60 kD. Nicalin was also detected in a 500- to 550-kD complex containing NOMO2. Nicalin and NOMO2 cofractionated with endoplasmic reticulum membranes.