ID   VKTH2_BUNFA             Reviewed;          85 AA.
AC   B2KTG3;
DT   16-JUN-2009, integrated into UniProtKB/Swiss-Prot.
DT   10-JUN-2008, sequence version 1.
DT   25-MAY-2022, entry version 37.
DE   RecName: Full=Kunitz-type serine protease inhibitor homolog beta-bungarotoxin BF B2 chain;
DE   Flags: Precursor;
OS   Bungarus fasciatus (Banded krait) (Pseudoboa fasciata).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC   Serpentes; Colubroidea; Elapidae; Bungarinae; Bungarus.
OX   NCBI_TaxID=8613;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   TISSUE=Venom gland;
RX   PubMed=18164783; DOI=10.1016/j.peptides.2007.11.013;
RA   Lu J., Yang H., Yu H., Gao W., Lai R., Liu J., Liang X.;
RT   "A novel serine protease inhibitor from Bungarus fasciatus venom.";
RL   Peptides 29:369-374(2008).
CC   -!- FUNCTION: Beta-1-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 blocks voltage-gated potassium channels
CC       (Kv) (By similarity). {ECO:0000250}.
CC   -!- SUBUNIT: Heterodimer; disulfide-linked. The A chains have phospholipase
CC       A2 activity and the B chains show 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   ---------------------------------------------------------------------------
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; EU220209; ABY71038.1; -; mRNA.
DR   AlphaFoldDB; B2KTG3; -.
DR   SMR; B2KTG3; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0015459; F:potassium channel regulator activity; IEA:UniProtKB-KW.
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; Ion channel impairing toxin; Neurotoxin;
KW   Potassium channel impairing toxin; Presynaptic neurotoxin; Secreted;
KW   Signal; Toxin; Voltage-gated potassium channel impairing toxin.
FT   SIGNAL          1..24
FT                   /evidence="ECO:0000250"
FT   CHAIN           25..85
FT                   /note="Kunitz-type serine protease inhibitor homolog beta-
FT                   bungarotoxin BF B2 chain"
FT                   /id="PRO_0000376876"
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;  9506 MW;  10A52419CBF3F8A3 CRC64;
     MSSGGLLLLL GLLTLWAELT PISSRERHPD CDKPPDTGRC GNNVRAFYYK PSTNKCVQFI
     YGGCNANGNH FKSDHLCRCQ CREND