ID   3LKB_BUNCA              Reviewed;          87 AA.
AC   Q8AY55;
DT   13-APR-2004, integrated into UniProtKB/Swiss-Prot.
DT   01-MAR-2003, sequence version 1.
DT   25-MAY-2022, entry version 64.
DE   RecName: Full=Kappa 1b-bungarotoxin;
DE   Flags: Precursor;
OS   Bungarus candidus (Malayan krait).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC   Serpentes; Colubroidea; Elapidae; Bungarinae; Bungarus.
OX   NCBI_TaxID=92438;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   TISSUE=Venom gland;
RA   Tsai I.H., Wang Y.M., Hsu H.Y.;
RT   "Structural and functional genomics of Bungarus candidus.";
RL   Submitted (OCT-2001) to the EMBL/GenBank/DDBJ databases.
CC   -!- FUNCTION: Postsynaptic neurotoxin that binds and inhibits neuronal
CC       nicotinic acetylcholine receptors (nAChR) with high affinity
CC       (IC(50)<100 nM). Is a selective, and slowly reversible antagonist of
CC       alpha-3/CHRNA3-containing and some alpha-4/CHRNA4-containing AChRs.
CC       {ECO:0000250|UniProtKB:P01398}.
CC   -!- SUBUNIT: Homo- and heterodimer; non-covalently linked.
CC       {ECO:0000250|UniProtKB:P15816}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000250}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland. {ECO:0000305}.
CC   -!- SIMILARITY: Belongs to the snake three-finger toxin family. Long-chain
CC       subfamily. Kappa-neurotoxin sub-subfamily. {ECO:0000305}.
CC   ---------------------------------------------------------------------------
CC   Copyrighted by the UniProt Consortium, see https://www.uniprot.org/terms
CC   Distributed under the Creative Commons Attribution (CC BY 4.0) License
CC   ---------------------------------------------------------------------------
DR   EMBL; AY057873; AAL30055.1; -; mRNA.
DR   AlphaFoldDB; Q8AY55; -.
DR   BMRB; Q8AY55; -.
DR   SMR; Q8AY55; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0030550; F:acetylcholine receptor inhibitor activity; IEA:UniProtKB-KW.
DR   GO; GO:0099106; F:ion channel regulator activity; IEA:UniProtKB-KW.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   CDD; cd00206; snake_toxin; 1.
DR   Gene3D; 2.10.60.10; -; 1.
DR   InterPro; IPR003571; Snake_3FTx.
DR   InterPro; IPR045860; Snake_toxin-like_sf.
DR   InterPro; IPR018354; Snake_toxin_con_site.
DR   SUPFAM; SSF57302; SSF57302; 1.
DR   PROSITE; PS00272; SNAKE_TOXIN; 1.
PE   3: Inferred from homology;
KW   Acetylcholine receptor inhibiting toxin; Disulfide bond;
KW   Ion channel impairing toxin; Neurotoxin; Postsynaptic neurotoxin; Secreted;
KW   Signal; Toxin.
FT   SIGNAL          1..21
FT                   /evidence="ECO:0000250"
FT   CHAIN           22..87
FT                   /note="Kappa 1b-bungarotoxin"
FT                   /id="PRO_0000035409"
FT   DISULFID        24..42
FT                   /evidence="ECO:0000250|UniProtKB:P01398"
FT   DISULFID        35..63
FT                   /evidence="ECO:0000250|UniProtKB:P01398"
FT   DISULFID        48..52
FT                   /evidence="ECO:0000250|UniProtKB:P01398"
FT   DISULFID        67..79
FT                   /evidence="ECO:0000250|UniProtKB:P01398"
FT   DISULFID        80..85
FT                   /evidence="ECO:0000250|UniProtKB:P01398"
SQ   SEQUENCE   87 AA;  9522 MW;  7FF8AD894FA7BFB5 CRC64;
     MKTLLLTLVV VTIVCLDLGY TRTCLISPSS TPQTCPQGQG ICFLKAQCDK FCSIRGPVIE
     QGCVATCPQF RSNYRSLLCC TTDNCNH