Dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit STT3B (Oligosaccharyl transferase subunit STT3B) (STT3-B) (EC 2.4.99.18) (Source of immunodominant MHC-associated peptides homolog)
1_MAEPS 6_ APESK 11_ HKSSL 16_ NSSPW 21_ SGLMA 26_ LGNSR 31_ HGHHG 36_ PGAQC 41_ AHKAA 46_ GGAAP 51_ PKPAP 56_ AGLSG 61_ GLSQP 66_ AGWQS 71_ LLSFT 76_ ILFLA 81_ WLAGF 86_ SSRLF 91_ AVIRF 96_ ESIIH 101_ EFDPW 106_ FNYRS 111_ THHLA 116_ SHGFY 121_ EFLNW 126_ FDERA 131_ WYPLG 136_ RIVGG 141_ TVYPG 146_ LMITA 151_ GLIHW 156_ ILNTL 161_ NITVH 166_ IRDVC 171_ VFLAP 176_ TFSGL 181_ TSIST 186_ FLLTR 191_ ELWNQ 196_ GAGLL 201_ AACFI 206_ AIVPG 211_ YISRS 216_ VAGSF 221_ DNEGI 226_ AIFAL 231_ QFTYY 236_ LWVKS 241_ VKTGS 246_ VFWTM 251_ CCCLS 256_ YFYMV 261_ SAWGG 266_ YVFII 271_ NLIPL 276_ HVFVL 281_ LLMQR 286_ YSKRV 291_ YIAYS 296_ TFYIV 301_ GLILS 306_ MQIPF 311_ VGFQP 316_ IRTSE 321_ HMAAA 326_ GVFAL 331_ LQAYA 336_ FLQYL 341_ RDRLT 346_ KQEFQ 351_ TLFFL 356_ GVSLA 361_ AGAVF 366_ LSVIY 371_ LTYTG 376_ YIAPW 381_ SGRFY 386_ SLWDT 391_ GYAKI 396_ HIPII 401_ ASVSE 406_ HQPTT 411_ WVSFF 416_ FDLHI 421_ LVCTF 426_ PAGLW 431_ FCIKN 436_ INDER 441_ VFVAL 446_ YAISA 451_ VYFAG 456_ VMVRL 461_ MLTLT 466_ PVVCM 471_ LSAIA 476_ FSNVF 481_ EHYLG 486_ DDMKR 491_ ENPPV 496_ EDSSD 501_ EDDKR 506_ NQGNL 511_ YDKAG 516_ KVRKH 521_ ATEQE 526_ KTEEG 531_ LGPNI 536_ KSIVT 541_ MLMLM 546_ LLMMF 551_ AVHCT 556_ WVTSN 561_ AYSSP 566_ SVVLA 571_ SYNHD 576_ GTRNI 581_ LDDFR 586_ EAYFW 591_ LRQNT 596_ DEHAR 601_ VMSWW 606_ DYGYQ 611_ IAGMA 616_ NRTTL 621_ VDNNT 626_ WNNSH 631_ IALVG 636_ KAMSS 641_ NETAA 646_ YKIMR 651_ TLDVD 656_ YVLVI 661_ FGGVI 666_ GYSGD 671_ DINKF 676_ LWMVR 681_ IAEGE 686_ HPKDI 691_ RESDY 696_ FTPQG 701_ EFRVD 706_ KAGSP 711_ TLLNC 716_ LMYKM 721_ SYYRF 726_ GEMQL 731_ DFRTP 736_ PGFDR 741_ TRNAE 746_ IGNKD 751_ IKFKH 756_ LEEAF 761_ TSEHW 766_ LVRIY 771_ KVKAP 776_ DNRET 781_ LDHKP 786_ RVTNI 791_ FPKQK 796_ YLSKK 801_ TTKRK 806_ RGYIK 811_ NKLVF 816_ KKGKK 821_ISKKT
1: Catalytic subunit of the oligosaccharyl transferase (OST) complex that catalyzes the initial transfer of a defined glycan (Glc(3)Man(9)GlcNAc(2) in eukaryotes) from the lipid carrier dolichol-pyrophosphate to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains, the first step in protein N-glycosylation (PubMed:19167329, PubMed:31296534, PubMed:31831667, PubMed:39509507). N-glycosylation occurs cotranslationally and the complex associates with the Sec61 complex at the channel-forming translocon complex that mediates protein translocation across the endoplasmic reticulum (ER) (PubMed:19167329, PubMed:31296534, PubMed:31831667, PubMed:39509507). All subunits are required for a maximal enzyme activity. This subunit contains the active site and the acceptor peptide and donor lipid-linked oligosaccharide (LLO) binding pockets (PubMed:19167329, PubMed:31296534, PubMed:31831667, PubMed:39509507). STT3B is present in a small subset of OST complexes (OST-B) and mediates both cotranslational and post-translational N-glycosylation of target proteins: STT3B-containing complexes are required for efficient post-translational glycosylation and while they are less competent than STT3A-containing complexes for cotranslational glycosylation, they have the ability to mediate glycosylation of some nascent sites that are not accessible for STT3A (PubMed:19167329, PubMed:22607976, PubMed:31296534, PubMed:39509507). STT3B-containing complexes also act post-translationally and mediate modification of skipped glycosylation sites in unfolded proteins (PubMed:19167329, PubMed:22607976, PubMed:39509507). Plays a role in ER-associated degradation (ERAD) pathway that mediates ubiquitin-dependent degradation of misfolded endoplasmic reticulum proteins by mediating N-glycosylation of unfolded proteins, which are then recognized by the ERAD pathway and targeted for degradation (PubMed:19167329, PubMed:22607976). Mediates glycosylation of the disease variant AMYL-TTR 'Asp-38' of TTR at 'Asn-118', leading to its degradation (PubMed:19167329, PubMed:22607976)