ID   VKT4_HETMG              Reviewed;          72 AA.
AC   A0A3G2FQK2;
DT   29-SEP-2021, integrated into UniProtKB/Swiss-Prot.
DT   13-FEB-2019, sequence version 1.
DT   03-AUG-2022, entry version 14.
DE   RecName: Full=PI-stichotoxin-Hmg3d {ECO:0000305};
DE            Short=PI-SHTX-Hmg3d {ECO:0000305};
DE   AltName: Full=IQ-peptide {ECO:0000303|Ref.1};
DE   AltName: Full=Kunitz-type serine protease inhibitor HMIQ3c1 {ECO:0000303|Ref.1};
DE   Flags: Precursor; Fragment;
OS   Heteractis magnifica (Magnificent sea anemone) (Radianthus magnifica).
OC   Eukaryota; Metazoa; Cnidaria; Anthozoa; Hexacorallia; Actiniaria;
OC   Stichodactylidae; Heteractis.
OX   NCBI_TaxID=38281;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], FUNCTION, AND RECOMBINANT EXPRESSION.
RX   DOI=10.1134/S106816201804012X;
RA   Kvetkina A.N., Leychenko E.V., Yurchenko E.A., Pislyagin E.A., Peigneur S.,
RA   Tytgat Y., Isaeva M.P., Aminin D.L., Kozlovskaya E.P.;
RT   "New IQ-peptide of the Kunitz-type from the Heteractis magnifica sea
RT   anemone exhibits neuroprotective activity in a model of Alzheimer's
RT   disease.";
RL   Russ. J. Bioorg. Chem. 44:416-423(2018).
CC   -!- FUNCTION: Serine protease inhibitor that inhibits trypsin (Ki=50 nM).
CC       This protease exhibits a pronounced neuroprotective activity on
CC       Alzheimer's disease model. It enhances cell viability by 39.4% when
CC       neuroblastoma cells are in presence of the toxin component beta-
CC       amyloid, but has no effect when these cells are in presence of 6-OHDA.
CC       {ECO:0000269|Ref.1}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000250|UniProtKB:P0DMJ5}.
CC       Nematocyst {ECO:0000250|UniProtKB:P0DMJ5}.
CC   -!- MISCELLANEOUS: Does not show activity on the eight potassium channels
CC       tested (Kv1.1/KCNA1, Kv1.2/KCNA2, Kv1.3/KCNA3, Kv1.4/KCNA4,
CC       Kv1.5/KCNA5, Kv1.6/KCNA8, Shaker IR, and Kv11.1/KCNH2/ERG1).
CC       {ECO:0000269|Ref.1}.
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   EMBL; MG788754; AYM94129.1; -; mRNA.
DR   SMR; A0A3G2FQK2; -.
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   2: Evidence at transcript level;
KW   Cleavage on pair of basic residues; Disulfide bond; Nematocyst;
KW   Protease inhibitor; Secreted; Serine protease inhibitor; Signal.
FT   SIGNAL          <1..14
FT                   /evidence="ECO:0000255"
FT   CHAIN           15..72
FT                   /note="PI-stichotoxin-Hmg3d"
FT                   /evidence="ECO:0000305"
FT                   /id="PRO_0000453393"
FT   DOMAIN          20..70
FT                   /note="BPTI/Kunitz inhibitor"
FT                   /evidence="ECO:0000255"
FT   DISULFID        20..70
FT                   /evidence="ECO:0000250|UniProtKB:P31713"
FT   DISULFID        29..53
FT                   /evidence="ECO:0000250|UniProtKB:P31713"
FT   DISULFID        45..66
FT                   /evidence="ECO:0000250|UniProtKB:P31713"
FT   NON_TER         1
FT                   /evidence="ECO:0000305|Ref.1"
SQ   SEQUENCE   72 AA;  8238 MW;  9CE0CDFCBBDE7114 CRC64;
     GFYFRSIQGF YFKRIQGNIC SEPKKVGRCR GSFPRFYFDS ETGKCTPFIY GGCGGNGNNF
     ETLRRCRAIC RA