VKTH1_BUNMU
ID VKTH1_BUNMU Reviewed; 85 AA.
AC P00987; O42298; P00988; Q9PTA4;
DT 21-JUL-1986, integrated into UniProtKB/Swiss-Prot.
DT 15-JUL-1998, sequence version 2.
DT 25-MAY-2022, entry version 108.
DE RecName: Full=Kunitz-type serine protease inhibitor homolog beta-bungarotoxin B1 chain, major component;
DE AltName: Full=Beta-1-bungarotoxin;
DE Flags: Precursor;
OS Bungarus multicinctus (Many-banded krait).
OC Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC Serpentes; Colubroidea; Elapidae; Bungarinae; Bungarus.
OX NCBI_TaxID=8616;
RN [1]
RP NUCLEOTIDE SEQUENCE [MRNA], AND FUNCTION.
RC TISSUE=Venom gland;
RX PubMed=9693106; DOI=10.1042/bj3340087;
RA Wu P.-F., Wu S.-N., Chang C.-C., Chang L.-S.;
RT "Cloning and functional expression of B chains of beta-bungarotoxins from
RT Bungarus multicinctus (Taiwan banded krait).";
RL Biochem. J. 334:87-92(1998).
RN [2]
RP NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC TISSUE=Liver;
RX PubMed=10903499; DOI=10.1046/j.1432-1327.2000.01518.x;
RA Wu P.-F., Chang L.-S.;
RT "Genetic organization of A chain and B chain of beta-bungarotoxin from
RT Taiwan banded krait (Bungarus multicinctus). A chain genes and B chain
RT genes do not share a common origin.";
RL Eur. J. Biochem. 267:4668-4675(2000).
RN [3]
RP PROTEIN SEQUENCE OF 25-85.
RC TISSUE=Venom;
RX PubMed=624701; DOI=10.1093/oxfordjournals.jbchem.a131881;
RA Kondo K., Narita K., Lee C.-Y.;
RT "Amino acid sequences of the two polypeptide chains in beta1-bungarotoxin
RT from the venom of Bungarus multicinctus.";
RL J. Biochem. 83:101-115(1978).
RN [4]
RP MUTAGENESIS OF CYS-79.
RX PubMed=11732693; DOI=10.1023/a:1012237005574;
RA Wu P.-F., Chang L.-S.;
RT "Expression of A chain and B chain of beta-bungarotoxin from taiwan banded
RT krait: the functional implication of the interchain disulfide bond between
RT A chain and B chain.";
RL J. Protein Chem. 20:413-421(2001).
RN [5]
RP SUBUNIT.
RC TISSUE=Venom;
RX PubMed=16457863; DOI=10.1016/j.toxicon.2005.11.009;
RA Cheng Y.-C., Chen K.-C., Lin S.-K., Chang L.-S.;
RT "Divergence of genes encoding B chains of beta-bungarotoxins.";
RL Toxicon 47:322-329(2006).
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, ECO:0000269|PubMed:9693106}.
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. {ECO:0000269|PubMed:16457863}.
CC -!- SUBCELLULAR LOCATION: Secreted.
CC -!- TISSUE SPECIFICITY: Expressed by the venom gland.
CC -!- SIMILARITY: Belongs to the venom Kunitz-type family. {ECO:0000305}.
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DR EMBL; Y12100; CAA72809.1; -; mRNA.
DR EMBL; AJ251223; CAB62503.1; -; Genomic_DNA.
DR PIR; A01219; TIKFBY.
DR AlphaFoldDB; P00987; -.
DR SMR; P00987; -.
DR MEROPS; I02.978; -.
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 1: Evidence at protein level;
KW Direct protein sequencing; Disulfide bond; Ion channel impairing toxin;
KW Neurotoxin; Potassium channel impairing toxin; Presynaptic neurotoxin;
KW Secreted; Signal; Toxin; Voltage-gated potassium channel impairing toxin.
FT SIGNAL 1..24
FT /evidence="ECO:0000269|PubMed:624701"
FT CHAIN 25..85
FT /note="Kunitz-type serine protease inhibitor homolog beta-
FT bungarotoxin B1 chain, major component"
FT /id="PRO_0000016863"
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 MUTAGEN 79
FT /note="C->S: Loss of PA2 activity. Weak loss in folding."
FT /evidence="ECO:0000269|PubMed:11732693"
FT CONFLICT 16
FT /note="C -> S (in Ref. 2; CAB62503)"
FT /evidence="ECO:0000305"
FT CONFLICT 45
FT /note="Missing (in Ref. 3; AA sequence)"
FT /evidence="ECO:0000305"
FT CONFLICT 65..70
FT /note="NGNGNH -> DGDHGN (in Ref. 3; AA sequence)"
FT /evidence="ECO:0000305"
SQ SEQUENCE 85 AA; 9571 MW; A1E3D452AE67DE5C CRC64;
MSSGGLLLLL GLLTLCAELI PVSSRQRHRD CDKPPDKGNC GPVRRAFYYD TRLKTCKAFQ
YRGCNGNGNH FKTETLCRCE CLVYP
