biostudies-literatureShrimal SNIGMS NIH HHS81-95https://www.ebi.ac.uk/biostudies/studies/S-EPMC3613688biostudies-literatureUnknown201(1)Metazoan organisms assemble two isoforms of the oligosaccharyltransferase (OST) that have different catalytic subunits (STT3A or STT3B) and partially nonoverlapping roles in asparagine-linked glycosylation. The STT3A isoform of the OST is primarily responsible for co-translational glycosylation of the nascent polypeptide as it enters the lumen of the endoplasmic reticulum. The C-terminal 65-75 residues of a glycoprotein will not contact the translocation channel-associated STT3A isoform of the OST complex before chain termination. Biosynthetic pulse labeling of five human glycoproteins showed that extreme C-terminal glycosylation sites were modified by an STT3B-dependent posttranslocational mechanism. The boundary for STT3B-dependent glycosylation of C-terminal sites was determined to fallThe Journal of cell biologyExtreme C-terminal sites are posttranslocationally glycosylated by the STT3B isoform of the OST.PMC3613688GM43687R01 GM043768Shrimal SGilmore RTrueman SFfalseExtreme C-terminal sites are posttranslocationally glycosylated by the STT3B isoform of the OST.Metazoan organisms assemble two isoforms of the oligosaccharyltransferase (OST) that have different catalytic subunits (STT3A or STT3B) and partially nonoverlapping roles in asparagine-linked glycosylation. The STT3A isoform of the OST is primarily responsible for co-translational glycosylation of the nascent polypeptide as it enters the lumen of the endoplasmic reticulum. The C-terminal 65-75 residues of a glycoprotein will not contact the translocation channel-associated STT3A isoform of the OST complex before chain termination. Biosynthetic pulse labeling of five human glycoproteins showed that extreme C-terminal glycosylation sites were modified by an STT3B-dependent posttranslocational mechanism. The boundary for STT3B-dependent glycosylation of C-terminal sites was determined to fall2013-01-01T00:00:00Z2013 Apr2026-05-04T04:07:20.71Z2019-03-27T01:06:48ZS-EPMC36136882353006610.1083/jcb.201301031