Complement C1r subcomponent (EC 3.4.21.41) (Complement component 1 subcomponent r) [Cleaved into: Complement C1r subcomponent heavy chain; Complement C1r subcomponent light chain]
1_MWLLY 6_ LLVPA 11_ LFCRA 16_ GGSIP 21_ IPQKL 26_ FGEVT 31_ SPLFP 36_ KPYPN 41_ NFETT 46_ TVITV 51_ PTGYR 56_ VKLVF 61_ QQFDL 66_ EPSEG 71_ CFYDY 76_ VKISA 81_ DKKSL 86_ GRFCG 91_ QLGSP 96_ LGNPP 101_ GKKEF 106_ MSQGN 111_ KMLLT 116_ FHTDF 121_ SNEEN 126_ GTIMF 131_ YKGFL 136_ AYYQA 141_ VDLDE 146_ CASRS 151_ KSGEE 156_ DPQPQ 161_ CQHLC 166_ HNYVG 171_ GYFCS 176_ CRPGY 181_ ELQED 186_ THSCQ 191_ AECSS 196_ ELYTE 201_ ASGYI 206_ SSLEY 211_ PRSYP 216_ PDLRC 221_ NYSIR 226_ VERGL 231_ TLHLK 236_ FLEPF 241_ DIDDH 246_ QQVHC 251_ PYDQL 256_ QIYAN 261_ GKNIG 266_ EFCGK 271_ QRPPD 276_ LDTSS 281_ NAVDL 286_ LFFTD 291_ ESGDS 296_ RGWKL 301_ RYTTE 306_ IIKCP 311_ QPKTL 316_ DEFTI 321_ IQNLQ 326_ PQYQF 331_ RDYFI 336_ ATCKQ 341_ GYQLI 346_ EGNQV 351_ LHSFT 356_ AVCQD 361_ DGTWH 366_ RAMPR 371_ CKIKD 376_ CGQPR 381_ NLPNG 386_ DFRYT 391_ TTMGV 396_ NTYKA 401_ RIQYY 406_ CHEPY 411_ YKMQT 416_ RAGSR 421_ ESEQG 426_ VYTCT 431_ AQGIW 436_ KNEQK 441_ GEKIP 446_ RCLPV 451_ CGKPV 456_ NPVEQ 461_ RQRII 466_ GGQKA 471_ KMGNF 476_ PWQVF 481_ TNIHG 486_ RGGGA 491_ LLGDR 496_ WILTA 501_ AHTLY 506_ PKEHE 511_ AQSNA 516_ SLDVF 521_ LGHTN 526_ VEELM 531_ KLGNH 536_ PIRRV 541_ SVHPD 546_ YRQDE 551_ SYNFE 556_ GDIAL 561_ LELEN 566_ SVTLG 571_ PNLLP 576_ ICLPD 581_ NDTFY 586_ DLGLM 591_ GYVSG 596_ FGVME 601_ EKIAH 606_ DLRFV 611_ RLPVA 616_ NPQAC 621_ ENWLR 626_ GKNRM 631_ DVFSQ 636_ NMFCA 641_ GHPSL 646_ KQDAC 651_ QGDSG 656_ GVFAV 661_ RDPNT 666_ DRWVA 671_ TGIVS 676_ WGIGC 681_ SRGYG 686_ FYTKV 691_ LNYVD 696_WIKKE
1: Serine protease component of the complement C1 complex, a multiprotein complex that initiates the classical pathway of the complement system, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system (PubMed:17996945, PubMed:19473974, PubMed:29449492). C1R catalyzes the first enzymatic step in the classical complement pathway: it is activated by the C1Q subcomplex of the C1 complex, which associates with IgG or IgM immunoglobulins complexed with antigens to form antigen-antibody complexes on the surface of pathogens (PubMed:29449492, PubMed:34155115). Immunoglobulin-binding promotes the autocatalytic cleavage and activation of C1R (PubMed:11445589, PubMed:11673533, PubMed:17996945, PubMed:20178990, PubMed:6254570, PubMed:6271784). Activated C1R then cleaves and activates C1S, the second protease of the classical complement pathway (PubMed:11445589, PubMed:11673533, PubMed:6271784). It is unclear if C1R activates C1S within single, strained C1 complexes or between neighboring C1 complexes on surfaces (PubMed:28104818, PubMed:29311313, PubMed:29449492)