Dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit STT3A (Oligosaccharyl transferase subunit STT3A) (STT3-A) (EC 2.4.99.18) (B5) (Integral membrane protein 1) (Transmembrane protein TMC)
1_MTKFG 6_ FLRLS 11_ YEKQD 16_ TLLKL 21_ LILSM 26_ AAVLS 31_ FSTRL 36_ FAVLR 41_ FESVI 46_ HEFDP 51_ YFNYR 56_ TTRFL 61_ AEEGF 66_ YKFHN 71_ WFDDR 76_ AWYPL 81_ GRIIG 86_ GTIYP 91_ GLMIT 96_ SAAIY 101_ HVLHF 106_ FHITI 111_ DIRNV 116_ CVFLA 121_ PLFSS 126_ FTTIV 131_ TYHLT 136_ KELKD 141_ AGAGL 146_ LAAAM 151_ IAVVP 156_ GYISR 161_ SVAGS 166_ YDNEG 171_ IAIFC 176_ MLLTY 181_ YMWIK 186_ AVKTG 191_ SICWA 196_ AKCAL 201_ AYFYM 206_ VSSWG 211_ GYVFL 216_ INLIP 221_ LHVLV 226_ LMLTG 231_ RFSHR 236_ IYVAY 241_ CTVYC 246_ LGTIL 251_ SMQIS 256_ FVGFQ 261_ PVLSS 266_ EHMAA 271_ FGVFG 276_ LCQIH 281_ AFVDY 286_ LRSKL 291_ NPQQF 296_ EVLFR 301_ SVISL 306_ VGFVL 311_ LTVGA 316_ LLMLT 321_ GKISP 326_ WTGRF 331_ YSLLD 336_ PSYAK 341_ NNIPI 346_ IASVS 351_ EHQPT 356_ TWSSY 361_ YFDLQ 366_ LLVFM 371_ FPVGL 376_ YYCFS 381_ NLSDA 386_ RIFII 391_ MYGVT 396_ SMYFS 401_ AVMVR 406_ LMLVL 411_ APVMC 416_ ILSGI 421_ GVSQV 426_ LSTYM 431_ KNLDI 436_ SRPDK 441_ KSKKQ 446_ QDSTY 451_ PIKNE 456_ VASGM 461_ ILVMA 466_ FFLIT 471_ YTFHS 476_ TWVTS 481_ EAYSS 486_ PSIVL 491_ SARGG 496_ DGSRI 501_ IFDDF 506_ REAYY 511_ WLRHN 516_ TPEDA 521_ KVMSW 526_ WDYGY 531_ QITAM 536_ ANRTI 541_ LVDNN 546_ TWNNT 551_ HISRV 556_ GQAMA 561_ STEEK 566_ AYEIM 571_ RELDV 576_ SYVLV 581_ IFGGL 586_ TGYSS 591_ DDINK 596_ FLWMV 601_ RIGGS 606_ TDTGK 611_ HIKEN 616_ DYYTP 621_ TGEFR 626_ VDREG 631_ SPVLL 636_ NCLMY 641_ KMCYY 646_ RFGQV 651_ YTEAK 656_ RPPGF 661_ DRVRN 666_ AEIGN 671_ KDFEL 676_ DVLEE 681_ AYTTE 686_ HWLVR 691_ IYKVK 696_DLDNR
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:34653363, PubMed:38670073, 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:34653363, PubMed:38670073, PubMed:39509507). All subunits are required for a maximal enzyme activity (PubMed:19167329, PubMed:31831667, PubMed:34653363). This subunit contains the active site and the acceptor peptide and donor lipid-linked oligosaccharide (LLO) binding pockets (PubMed:19167329). STT3A is present in the majority of OST complexes and mediates cotranslational N-glycosylation of most sites on target proteins, while STT3B-containing complexes are required for efficient post-translational glycosylation and mediate glycosylation of sites that have been skipped by STT3A (PubMed:19167329, PubMed:38670073, PubMed:39509507). STT3A-containing OST-A complex is also required to prevent hyperglycosylation of some target proteins by preventing glycosylation of facultative sites before folding of target proteins is completed (PubMed:39509507)