ID   VKTHB_BUNCA             Reviewed;          85 AA.
AC   Q8AY46;
DT   09-JAN-2007, integrated into UniProtKB/Swiss-Prot.
DT   09-JAN-2007, sequence version 2.
DT   25-MAY-2022, entry version 61.
DE   RecName: Full=Kunitz-type serine protease inhibitor homolog beta-bungarotoxin B1 chain;
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: Beta-bungarotoxin is a presynaptic neurotoxin of the venom.
CC       The B chain is homologous to venom basic protease inhibitors but has no
CC       protease inhibitor activity and is non-toxic (By similarity).
CC       {ECO:0000250}.
CC   -!- SUBUNIT: Heterodimer; disulfide-linked. The A chain has phospholipase
CC       A2 activity and the B chain shows homology with the basic protease
CC       inhibitors (By similarity). {ECO:0000250}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000250}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland.
CC   -!- SIMILARITY: Belongs to the venom Kunitz-type family. {ECO:0000305}.
CC   -!- SEQUENCE CAUTION:
CC       Sequence=AAL30065.1; Type=Erroneous initiation; Evidence={ECO:0000305};
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DR   EMBL; AY057883; AAL30065.1; ALT_INIT; mRNA.
DR   AlphaFoldDB; Q8AY46; -.
DR   SMR; Q8AY46; -.
DR   MEROPS; I02.978; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0004867; F:serine-type endopeptidase inhibitor activity; IEA:InterPro.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   CDD; cd00109; KU; 1.
DR   Gene3D; 4.10.410.10; -; 1.
DR   InterPro; IPR002223; Kunitz_BPTI.
DR   InterPro; IPR036880; Kunitz_BPTI_sf.
DR   InterPro; IPR020901; Prtase_inh_Kunz-CS.
DR   Pfam; PF00014; Kunitz_BPTI; 1.
DR   PRINTS; PR00759; BASICPTASE.
DR   SMART; SM00131; KU; 1.
DR   SUPFAM; SSF57362; SSF57362; 1.
DR   PROSITE; PS00280; BPTI_KUNITZ_1; 1.
DR   PROSITE; PS50279; BPTI_KUNITZ_2; 1.
PE   2: Evidence at transcript level;
KW   Disulfide bond; Neurotoxin; Presynaptic neurotoxin; Secreted; Signal;
KW   Toxin.
FT   SIGNAL          1..24
FT                   /evidence="ECO:0000250"
FT   CHAIN           25..85
FT                   /note="Kunitz-type serine protease inhibitor homolog beta-
FT                   bungarotoxin B1 chain"
FT                   /id="PRO_0000271459"
FT   DOMAIN          31..81
FT                   /note="BPTI/Kunitz inhibitor"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
FT   DISULFID        31..81
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
FT   DISULFID        40..64
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
FT   DISULFID        56..77
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
FT   DISULFID        79
FT                   /note="Interchain (with an A chain)"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
SQ   SEQUENCE   85 AA;  9518 MW;  A1F325B04C49115C CRC64;
     MSSGGLLLLL GLLTLCAELT PVSSRQRHRD CDKPPDKGNC GSVRRAFYYD TRLKTCKAFP
     YRGCNGNGNH FKTETLCRCE CLVYP