ID   VKT1_ANTAF              Reviewed;          58 AA.
AC   P81547;
DT   01-JUN-2001, integrated into UniProtKB/Swiss-Prot.
DT   01-MAR-2001, sequence version 1.
DT   25-MAY-2022, entry version 72.
DE   RecName: Full=PI-actitoxin-Axm2a {ECO:0000303|PubMed:22683676};
DE            Short=PI-AITX-Axm2a {ECO:0000303|PubMed:22683676};
DE   AltName: Full=Kunitz-type protease inhibitor AXPI-I {ECO:0000303|PubMed:9440231};
DE            Short=AXAPI {ECO:0000303|PubMed:18450492};
OS   Anthopleura aff. xanthogrammica (Sea anemone).
OC   Eukaryota; Metazoa; Cnidaria; Anthozoa; Hexacorallia; Actiniaria;
OC   Actiniidae; Anthopleura.
OX   NCBI_TaxID=152178;
RN   [1]
RP   PROTEIN SEQUENCE, FUNCTION, AND TISSUE SPECIFICITY.
RC   TISSUE=Tentacle;
RX   PubMed=9440231; DOI=10.1016/s0305-0491(97)00174-0;
RA   Minagawa S., Ishida M., Shimakura K., Nagashima Y., Shiomi K.;
RT   "Isolation and amino acid sequences of two Kunitz-type protease inhibitors
RT   from the sea anemone Anthopleura aff. xanthogrammica.";
RL   Comp. Biochem. Physiol. 118B:381-386(1997).
RN   [2]
RP   PROTEIN SEQUENCE, AND FUNCTION.
RX   PubMed=18450492; DOI=10.1016/j.cbpb.2008.03.010;
RA   Minagawa S., Sugiyama M., Ishida M., Nagashima Y., Shiomi K.;
RT   "Kunitz-type protease inhibitors from acrorhagi of three species of sea
RT   anemones.";
RL   Comp. Biochem. Physiol. 150B:240-245(2008).
RN   [3]
RP   NOMENCLATURE.
RX   PubMed=22683676; DOI=10.1016/j.toxicon.2012.05.020;
RA   Oliveira J.S., Fuentes-Silva D., King G.F.;
RT   "Development of a rational nomenclature for naming peptide and protein
RT   toxins from sea anemones.";
RL   Toxicon 60:539-550(2012).
CC   -!- FUNCTION: Serine protease inhibitor that is strongly active against
CC       trypsin (1900 IU/mg) and moderately active against plasmin. Also shows
CC       weak inhibition against chymotrypsin (70%), elastase (38%) and the
CC       metalloprotease thermolysin (14%). {ECO:0000269|PubMed:18450492,
CC       ECO:0000269|PubMed:9440231}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000305}. Nematocyst {ECO:0000305}.
CC   -!- TISSUE SPECIFICITY: Expressed by acrorhagi.
CC       {ECO:0000269|PubMed:18450492}.
CC   -!- MISCELLANEOUS: Does not inhibit potassium channels (Kv), as well as
CC       cysteine proteases (papain and bromelain) (PubMed:18450492). Is not
CC       active against kallikrein (PubMed:9440231).
CC       {ECO:0000305|PubMed:18450492, ECO:0000305|PubMed:9440231}.
CC   -!- SIMILARITY: Belongs to the venom Kunitz-type family. Sea anemone type 2
CC       potassium channel toxin subfamily. {ECO:0000305}.
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DR   AlphaFoldDB; P81547; -.
DR   SMR; P81547; -.
DR   MEROPS; I02.026; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0042151; C:nematocyst; IEA:UniProtKB-SubCell.
DR   GO; GO:0004867; F:serine-type endopeptidase inhibitor 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; Nematocyst; Protease inhibitor;
KW   Secreted; Serine protease inhibitor.
FT   CHAIN           1..58
FT                   /note="PI-actitoxin-Axm2a"
FT                   /evidence="ECO:0000269|PubMed:18450492,
FT                   ECO:0000269|PubMed:9440231"
FT                   /id="PRO_0000155416"
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 trypsin"
FT                   /evidence="ECO:0000250"
FT   DISULFID        7..57
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
FT   DISULFID        16..40
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
FT   DISULFID        32..53
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
SQ   SEQUENCE   58 AA;  6341 MW;  DA27216A535EA7CC CRC64;
     APVNEDCLLP KKVGPCRAAV PRFYYNSDSG KCEGFTYGGC HANANNFKTK DECKNACH