InterPro domain: IPR007676

Ribophorin I is an essential subunit of oligosaccharyltransferase (OST), which is also known as dolichyl-diphosphooligosaccharide--protein glycosyltransferase, ( 2.4.1.119 ). OST catalyses the transfer of an oligosaccharide from dolichol pyrophosphate to selected asparagine residues of nascent polypeptides as they are translocated into the lumen of the rough endoplasmic reticulum. In the past Ribophorin I and OST48 were thought to be responsible for OST catalytic activity [ 1 ], it is in reality the OST STTs subunits that are responsible for this activity [ 2 ]. Both yeast and mammalian proteins are glycosylated but the sites are not conserved. Glycosylation may contribute towards general solubility but is unlikely to be involved in a specific biochemical function [ 3 ]. Most family members are predicted to have a transmembrane helix at the C terminus of this region.

1. The oligosaccharyltransferase complex from pig liver: cDNA cloning, expression and functional characterisation. Glycoconj. J. 17, 767-79
2. Oligosaccharyltransferase: A Gatekeeper of Health and Tumor Progression. Int J Mol Sci 20
3. The essential yeast NLT1 gene encodes the 64 kDa glycoprotein subunit of the oligosaccharyl transferase. FEBS Lett. 362, 229-34