VKT9_BUNFA
ID VKT9_BUNFA Reviewed; 65 AA.
AC P25660;
DT 01-MAY-1992, integrated into UniProtKB/Swiss-Prot.
DT 01-MAY-1992, sequence version 1.
DT 25-MAY-2022, entry version 97.
DE RecName: Full=Kunitz-type serine protease inhibitor IX;
DE AltName: Full=Bungarus fasciatus fraction IX;
DE Short=BF9;
DE AltName: Full=Venom basic protease inhibitor IX;
DE Contains:
DE RecName: Full=Kunitz-type serine protease inhibitor VIIIB;
DE AltName: Full=Venom basic protease inhibitor VIIIB;
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 PROTEIN SEQUENCE.
RC TISSUE=Venom;
RX PubMed=6832893; DOI=10.1111/j.1399-3011.1983.tb03095.x;
RA Liu C.-S., Wu T.-C., Lo T.-B.;
RT "Complete amino acid sequences of two protease inhibitors in the venom of
RT Bungarus fasciatus.";
RL Int. J. Pept. Protein Res. 21:209-215(1983).
RN [2]
RP FUNCTION, AND MUTAGENESIS OF ASN-17 AND ALA-18.
RX PubMed=24243656; DOI=10.1002/jbt.21538;
RA Yang W., Feng J., Wang B., Cao Z., Li W., Wu Y., Chen Z.;
RT "BF9, the first functionally characterized snake toxin peptide with Kunitz-
RT type protease and potassium channel inhibiting properties.";
RL J. Biochem. Mol. Toxicol. 28:76-83(2014).
RN [3]
RP STRUCTURE BY NMR, DISULFIDE BONDS, AND FUNCTION.
RC TISSUE=Venom;
RX PubMed=11562364; DOI=10.1074/jbc.m106182200;
RA Chen C., Hsu C.-H., Su N.-Y., Lin Y.-C., Chiou S.-H., Wu S.-H.;
RT "Solution structure of a Kunitz-type chymotrypsin inhibitor isolated from
RT the elapid snake Bungarus fasciatus.";
RL J. Biol. Chem. 276:45079-45087(2001).
CC -!- FUNCTION: Dual-function toxin that inhibits both serine proteases (high
CC activity on chymotrypsin (Ki = 18 nM), and low activity on elastase)
CC and voltage-gated potassium channels Kv1.3/KCNA3 (IC(50) = 120.0 nM).
CC {ECO:0000269|PubMed:11562364, ECO:0000269|PubMed:24243656}.
CC -!- SUBCELLULAR LOCATION: Secreted.
CC -!- TISSUE SPECIFICITY: Expressed by the venom gland.
CC -!- MISCELLANEOUS: Does not show inhibitory effect on trypsin.
CC {ECO:0000305|PubMed:24243656}.
CC -!- SIMILARITY: Belongs to the venom Kunitz-type family. {ECO:0000305}.
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DR PDB; 1JC6; NMR; -; A=1-65.
DR PDBsum; 1JC6; -.
DR AlphaFoldDB; P25660; -.
DR SMR; P25660; -.
DR MEROPS; I02.031; -.
DR EvolutionaryTrace; P25660; -.
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:UniProtKB-KW.
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 3D-structure; Direct protein sequencing; Disulfide bond;
KW Ion channel impairing toxin; Potassium channel impairing toxin;
KW Protease inhibitor; Secreted; Serine protease inhibitor; Toxin;
KW Voltage-gated potassium channel impairing toxin.
FT CHAIN 1..65
FT /note="Kunitz-type serine protease inhibitor IX"
FT /id="PRO_0000016861"
FT CHAIN 1..62
FT /note="Kunitz-type serine protease inhibitor VIIIB"
FT /id="PRO_0000016862"
FT DOMAIN 7..57
FT /note="BPTI/Kunitz inhibitor"
FT /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
FT SITE 17..18
FT /note="Reactive bond for chymotrypsin"
FT DISULFID 7..57
FT /evidence="ECO:0000255|PROSITE-ProRule:PRU00031,
FT ECO:0000269|PubMed:11562364"
FT DISULFID 16..40
FT /evidence="ECO:0000255|PROSITE-ProRule:PRU00031,
FT ECO:0000269|PubMed:11562364"
FT DISULFID 32..53
FT /evidence="ECO:0000255|PROSITE-ProRule:PRU00031,
FT ECO:0000269|PubMed:11562364"
FT MUTAGEN 17
FT /note="N->K: Increase in trypsin and chymotrypsin
FT inhibitory activities. Complete loss of elastase inhibitory
FT activity."
FT /evidence="ECO:0000269|PubMed:24243656"
FT MUTAGEN 17
FT /note="N->L: Increase in chymotrypsin and elastase
FT inhibitory activities. No change in trypsin inhibitory
FT activity."
FT /evidence="ECO:0000269|PubMed:24243656"
FT MUTAGEN 18
FT /note="A->F: Complete loss of chymotrypsin and elastase
FT inhibitory activity. No change in trypsin inhibitory
FT activity."
FT /evidence="ECO:0000269|PubMed:24243656"
FT HELIX 6..8
FT /evidence="ECO:0007829|PDB:1JC6"
FT STRAND 22..26
FT /evidence="ECO:0007829|PDB:1JC6"
FT TURN 27..30
FT /evidence="ECO:0007829|PDB:1JC6"
FT STRAND 31..35
FT /evidence="ECO:0007829|PDB:1JC6"
FT STRAND 47..49
FT /evidence="ECO:0007829|PDB:1JC6"
FT HELIX 50..56
FT /evidence="ECO:0007829|PDB:1JC6"
SQ SEQUENCE 65 AA; 7294 MW; BA340749E194DB51 CRC64;
KNRPTFCNLL PETGRCNALI PAFYYNSHLH KCQKFNYGGC GGNANNFKTI DECQRTCAAK
YGRSS
