ID   ISIK_HELPO              Reviewed;          58 AA.
AC   P00994;
DT   21-JUL-1986, integrated into UniProtKB/Swiss-Prot.
DT   21-JUL-1986, sequence version 1.
DT   25-MAY-2022, entry version 87.
DE   RecName: Full=Isoinhibitor K;
OS   Helix pomatia (Roman snail) (Edible snail).
OC   Eukaryota; Metazoa; Spiralia; Lophotrochozoa; Mollusca; Gastropoda;
OC   Heterobranchia; Euthyneura; Panpulmonata; Eupulmonata; Stylommatophora;
OC   Helicina; Helicoidea; Helicidae; Helix.
OX   NCBI_TaxID=6536;
RN   [1]
RP   PROTEIN SEQUENCE, AND PYROGLUTAMATE FORMATION AT GLN-1.
RX   PubMed=1183446; DOI=10.1111/j.1432-1033.1975.tb02391.x;
RA   Tschesche H., Dietl T.;
RT   "The amino-acid sequence of isoinhibitor K form snails (Helix pomatia). A
RT   sequence determination by automated Edman degradation and mass-spectral
RT   identification of the phenylthiohydantoins.";
RL   Eur. J. Biochem. 58:439-451(1975).
RN   [2]
RP   DISULFIDE BONDS.
RX   PubMed=3462;
RA   Dietl T., Tschesche H.;
RT   "The disulfide bridges of the trypsin-kallikrein inhibitor K from snails
RT   (Helix pomatia). Thermal inactivation and proteolysis by thermolysin.";
RL   Hoppe-Seyler's Z. Physiol. Chem. 357:139-145(1976).
CC   -!- FUNCTION: This is one of several isoinhibitors of broad specificity
CC       that are secreted into the mucus of the snail.
CC   -!- SUBCELLULAR LOCATION: Secreted.
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DR   PIR; A91232; TIHABK.
DR   AlphaFoldDB; P00994; -.
DR   SMR; P00994; -.
DR   GO; GO:0005576; C:extracellular region; 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; Protease inhibitor;
KW   Pyrrolidone carboxylic acid; Secreted; Serine protease inhibitor.
FT   CHAIN           1..58
FT                   /note="Isoinhibitor K"
FT                   /id="PRO_0000155410"
FT   DOMAIN          7..57
FT                   /note="BPTI/Kunitz inhibitor"
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031"
FT   SITE            17..18
FT                   /note="Reactive bond"
FT                   /evidence="ECO:0000250"
FT   MOD_RES         1
FT                   /note="Pyrrolidone carboxylic acid"
FT                   /evidence="ECO:0000269|PubMed:1183446"
FT   DISULFID        7..57
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031,
FT                   ECO:0000269|PubMed:3462"
FT   DISULFID        16..40
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031,
FT                   ECO:0000269|PubMed:3462"
FT   DISULFID        32..53
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00031,
FT                   ECO:0000269|PubMed:3462"
SQ   SEQUENCE   58 AA;  6451 MW;  6796586C488453B7 CRC64;
     QGRPSFCNLP AETGPCKASF RQYYYNSKSG GCQQFIYGGC RGNQNRFDTT QQCQGVCV