Oligosaccharyltransferase complex subunit 4, non-catalytic, also called Dolichyl-diphosphooligosaccharide—protein glycosyltransferase subunit 4, is a protein that in humans is encoded by the OST4 gene. This protein is a subunit of the oligosaccharyltransferase complex.
OST4 is a very short, approximately 30 amino acids, protein found from fungi to vertebrates. It appears to be an integral membrane protein that mediates the en bloc transfer of a pre-assembled high-mannose oligosaccharide onto asparagine residues of nascent polypeptides as they enter the lumen of the rough endoplasmic reticulum.
See also Dolichyl-diphosphooligosaccharide–protein glycotransferase the enzyme class of the protein complex
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