Dolichyl-diphosphooligosaccharide–protein glycosyltransferase subunit STT3B (STT3B)

Dolichyl-diphosphooligosaccharide–protein glycosyltransferase subunit STT3B (STT3B) is a catalytic enzyme subunit of the oligosaccharyltransferase (OST) complex found in the endoplasmic reticulum membrane of eukaryotic cells[1][2][3][4][5]. Its main function is to catalyze the transfer of preassembled oligosaccharide chains from dolichyl-diphosphooligosaccharide donors onto asparagine residues within nascent polypeptides, a process called N-linked glycosylation[1][2][4]. Humans express two closely related OST catalytic subunits, STT3A and STT3B, which are assembled into distinct OST complexes and differ in substrate specificity and timing (co- vs post-translational modification)[1]. STT3B, in particular, mediates post-translational glycosylation of sites skipped by STT3A and acts independently of association with the protein translocation channel[1]. Mutations in STT3B can lead to congenital disorders of glycosylation and impact multiple systems due to insufficient protein glycosylation. STT3B is essential for proper protein folding and cell viability and represents a prototypical member of the glycosyltransferase family of enzymes that regulate glycoprotein expression, with implications in inherited and acquired disease[2][4].

Other names

STT3BDolichyl-diphosphooligosaccharide–protein glycosyltransferase subunit STT3BSIMPOligosaccharyl transferase subunit STT3BSTT3-BFLJ90106Source of immunodominant MHC-associated peptides homologCDG1XHomolog of yeast STT3Dolichyl-diphosphooligosaccharide protein glycotransferase

For potential or research inhibitors (e.g., tunicamycin): Inhibition of N-linked glycosylation by blocking dolichyl-diphosphooligosaccharide access or transfer activity of OST. Disruption of glycoprotein biosynthesis, leading to unfolded protein stress, ER stress, and apoptosis in susceptible cells.