Complement factor B (EC 3.4.21.47) (C3/C5 convertase) (Glycine-rich beta glycoprotein) (GBG) (PBF2) (Properdin factor B) [Cleaved into: Complement factor B Ba fragment; Complement factor B Bb fragment]
1_MGSNL 6_ SPQLC 11_ LMPFI 16_ LGLLS 21_ GGVTT 26_ TPWSL 31_ ARPQG 36_ SCSLE 41_ GVEIK 46_ GGSFR 51_ LLQEG 56_ QALEY 61_ VCPSG 66_ FYPYP 71_ VQTRT 76_ CRSTG 81_ SWSTL 86_ KTQDQ 91_ KTVRK 96_ AECRA 101_ IHCPR 106_ PHDFE 111_ NGEYW 116_ PRSPY 121_ YNVSD 126_ EISFH 131_ CYDGY 136_ TLRGS 141_ ANRTC 146_ QVNGR 151_ WSGQT 156_ AICDN 161_ GAGYC 166_ SNPGI 171_ PIGTR 176_ KVGSQ 181_ YRLED 186_ SVTYH 191_ CSRGL 196_ TLRGS 201_ QRRTC 206_ QEGGS 211_ WSGTE 216_ PSCQD 221_ SFMYD 226_ TPQEV 231_ AEAFL 236_ SSLTE 241_ TIEGV 246_ DAEDG 251_ HGPGE 256_ QQKRK 261_ IVLDP 266_ SGSMN 271_ IYLVL 276_ DGSDS 281_ IGASN 286_ FTGAK 291_ KCLVN 296_ LIEKV 301_ ASYGV 306_ KPRYG 311_ LVTYA 316_ TYPKI 321_ WVKVS 326_ EADSS 331_ NADWV 336_ TKQLN 341_ EINYE 346_ DHKLK 351_ SGTNT 356_ KKALQ 361_ AVYSM 366_ MSWPD 371_ DVPPE 376_ GWNRT 381_ RHVII 386_ LMTDG 391_ LHNMG 396_ GDPIT 401_ VIDEI 406_ RDLLY 411_ IGKDR 416_ KNPRE 421_ DYLDV 426_ YVFGV 431_ GPLVN 436_ QVNIN 441_ ALASK 446_ KDNEQ 451_ HVFKV 456_ KDMEN 461_ LEDVF 466_ YQMID 471_ ESQSL 476_ SLCGM 481_ VWEHR 486_ KGTDY 491_ HKQPW 496_ QAKIS 501_ VIRPS 506_ KGHES 511_ CMGAV 516_ VSEYF 521_ VLTAA 526_ HCFTV 531_ DDKEH 536_ SIKVS 541_ VGGEK 546_ RDLEI 551_ EVVLF 556_ HPNYN 561_ INGKK 566_ EAGIP 571_ EFYDY 576_ DVALI 581_ KLKNK 586_ LKYGQ 591_ TIRPI 596_ CLPCT 601_ EGTTR 606_ ALRLP 611_ PTTTC 616_ QQQKE 621_ ELLPA 626_ QDIKA 631_ LFVSE 636_ EEKKL 641_ TRKEV 646_ YIKNG 651_ DKKGS 656_ CERDA 661_ QYAPG 666_ YDKVK 671_ DISEV 676_ VTPRF 681_ LCTGG 686_ VSPYA 691_ DPNTC 696_ RGDSG 701_ GPLIV 706_ HKRSR 711_ FIQVG 716_ VISWG 721_ VVDVC 726_ KNQKR 731_ QKQVP 736_ AHARD 741_ FHINL 746_ FQVLP 751_ WLKEK 756_LQDED
1: Precursor of the catalytic component of the C3 and C5 convertase complexes of the alternative 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:3638964, PubMed:624565, PubMed:6554279, PubMed:6919543, PubMed:9748277). The alternative complement pathway acts as an amplification loop that enhances other complement pathways (classical, lectin and GZMK) by promoting formation of additional C3 and C5 convertases (PubMed:3638964, PubMed:624565, PubMed:6554279, PubMed:6919543, PubMed:9748277). CFB is cleaved and activated by CFD to generate Ba and Bb chains; Bb chain constituting the catalytic component of the C3 and C5 convertases (PubMed:6769474, PubMed:9748277)
2: Serine protease component of the complement C3 and C5 convertase complexes of the alternative complement pathway (PubMed:30643019, PubMed:3638964, PubMed:624565, PubMed:6554279, PubMed:6919543). Following cleavage and activation by factor D (CFD), forms the C3 convertase together with complement C3b (PubMed:3638964, PubMed:624565, PubMed:6554279, PubMed:6919543, PubMed:9748277). As part of the C3 convertase, cleaves and activates C3 into C3a anaphylatoxin and C3b opsonin, the next components of the complement pathways (PubMed:3638964, PubMed:624565, PubMed:6554279, PubMed:6919543, PubMed:9748277). When an additional complement C3b molecule binds to the C3 convertase, forms the C5 convertase, which cleaves and activates C5 into C5a anaphylatoxin and C5b component of the membrane attack complex (PubMed:30643019, PubMed:624565, PubMed:6554279)
3: Involved in proliferation and differentiation of preactivated B-lymphocytes, rapid spreading of peripheral blood monocytes, stimulation of lymphocyte blastogenesis and lysis of erythrocytes