N-oligosaccharyl transferase (OST)

Function: 1) catalyzes transfer of a high mannose oligosaccharide from a dolichol-linked oligosaccharide donor to an Asn within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains 2) N-glycosylation occurs cotranslational 3) associates with the Sec61 complex at the channel-forming translocon complex that mediates protein translocation across the endoplasmic reticulum Structure: - consists of: - RPN1, RPN2, OST48, DAD1, & either STT3A or STT3B - OST4 may also be associated Compartment: endoplasmic reticulum membrane Expression: - expressed in placenta, liver, muscle, pancreas > brain, lung & kidney - expressed in skin fibroblasts

General

glycosyltransferase molecular complex

Properties

MOTIF: active site SUBUNITS: dolichyl-diphosphooligosaccharide-protein glycosyltransferase subunit STT3A COMPARTMENT: endoplasmic reticulum MOTIF: cytoplasmic domain {1-17} transmembrane domain {18-38} exoplasmic loop {39-114} transmembrane domain {115-135} cytoplasmic loop {136-169} transmembrane domain {170-190} exoplasmic loop {191-208} transmembrane domain {209-229} cytoplasmic loop {230-235} transmembrane domain {236-259} exoplasmic loop {260-300} transmembrane domain {301-321} cytoplasmic loop {322-359} transmembrane domain {360-380} exoplasmic loop {381-383} transmembrane domain {384-404} cytoplasmic loop {405-405} transmembrane domain {406-426} exoplasmic loop {427-453} transmembrane domain {454-474} cytoplasmic domain {475-705} MOTIF: N-glycosylation site {N537} N-glycosylation site {N544} N-glycosylation site {N548} ribophorin-1 COMPARTMENT: endoplasmic reticulum MOTIF: signal sequence {1-23} N-glycosylation site {N299} transmembrane domain {439-457} ribophorin-2 COMPARTMENT: endoplasmic reticulum MOTIF: exoplasmic domain {1-540} MOTIF: signal sequence {1-22} N-glycosylation site {N106} Thr phosphorylation site {T282} transmembrane domain {541-561} cytoplasmic loop {562-571} transmembrane domain {572-592} exoplasmic loop {593-596} transmembrane domain {597-617} cytoplasmic domain {618-631} oligosaccharyl transferase p48 subunit COMPARTMENT: endoplasmic reticulum MOTIF: signal sequence {1-26} glycosylation site transmembrane domain {411-430} dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit DAD1 COMPARTMENT: cellular membrane MOTIF: acetylation site SITE: N-TERMINUS EFFECTOR-BOUND: acetyl transmembrane domain {31-51} transmembrane domain {53-73} dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit 4 COMPARTMENT: cellular membrane MOTIF: transmembrane domain {5-25}

References

UniProt :accession P46977

Components

dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit 4 (OST4) dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit DAD1; oligosaccharyl transferase subunit DAD1; defender against cell death 1; DAD-1 (DAD1) dolichyl-diphosphooligosaccharide-protein glycosyltransferase subunit STT3A; oligosaccharyl transferase subunit STT3A; STT3-A; B5; integral membrane protein 1 (TMC, STT3A, ITM1) oligosaccharyl transferase p48 subunit; dolichyl-diphosphooligosaccharide-protein glycosyltransferase 48 kD subunit precursor; DDOST 48 kD subunit (DDOST, KIAA0115, OST48, OK/SW-cl.45) ribophorin-1; dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit 1; dolichyl-diphosphooligosaccharide--protein glycosyltransferase 67 kD subunit; ribophorin I; RPN-I (RPN1) ribophorin-2; dolichyl-diphosphooligosaccharide-protein glycosyltransferase subunit 2; dolichyl-diphosphooligosaccharide-protein glycosyltransferase 63 kD subunit; RIBIIR; RPN-II (RPN2)