ID   ITR3_CUCPE              Reviewed;          32 AA.
AC   P10293;
DT   01-JUL-1989, integrated into UniProtKB/Swiss-Prot.
DT   01-JUL-1989, sequence version 1.
DT   25-MAY-2022, entry version 100.
DE   RecName: Full=Trypsin inhibitor 3;
DE   AltName: Full=CPTI-III;
DE   AltName: Full=Trypsin inhibitor III;
DE   Contains:
DE     RecName: Full=Trypsin inhibitor 2;
DE     AltName: Full=CPTI-II;
DE     AltName: Full=Trypsin inhibitor II;
OS   Cucurbita pepo (Vegetable marrow) (Summer squash).
OC   Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC   Spermatophyta; Magnoliopsida; eudicotyledons; Gunneridae; Pentapetalae;
OC   rosids; fabids; Cucurbitales; Cucurbitaceae; Cucurbiteae; Cucurbita.
OX   NCBI_TaxID=3663;
RN   [1]
RP   PROTEIN SEQUENCE.
RC   TISSUE=Seed;
RX   PubMed=3977882; DOI=10.1016/0006-291x(85)90233-5;
RA   Wieczorek M., Otlewski J., Cook J., Parks K., Leluk J., Wilimowska-Pelc A.,
RA   Polanowski A., Wilusz T., Laskowski M. Jr.;
RT   "The squash family of serine proteinase inhibitors. Amino acid sequences
RT   and association equilibrium constants of inhibitors from squash, summer
RT   squash, zucchini, and cucumber seeds.";
RL   Biochem. Biophys. Res. Commun. 126:646-652(1985).
CC   -!- FUNCTION: Inhibits trypsin.
CC   -!- SUBCELLULAR LOCATION: Secreted.
CC   -!- DOMAIN: The presence of a 'disulfide through disulfide knot'
CC       structurally defines this protein as a knottin. {ECO:0000250}.
CC   -!- SIMILARITY: Belongs to the protease inhibitor I7 (squash-type serine
CC       protease inhibitor) family. {ECO:0000305}.
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DR   PDB; 2BTC; X-ray; 1.50 A; I=4-32.
DR   PDB; 2STB; X-ray; 1.80 A; I=4-32.
DR   PDBsum; 2BTC; -.
DR   PDBsum; 2STB; -.
DR   AlphaFoldDB; P10293; -.
DR   SMR; P10293; -.
DR   MEROPS; I07.006; -.
DR   EvolutionaryTrace; P10293; -.
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; cd00150; PlantTI; 1.
DR   InterPro; IPR000737; Prot_inh_squash.
DR   InterPro; IPR011052; Proteinase_amylase_inhib_sf.
DR   Pfam; PF00299; Squash; 1.
DR   PRINTS; PR00293; SQUASHINHBTR.
DR   SUPFAM; SSF57027; SSF57027; 1.
DR   PROSITE; PS00286; SQUASH_INHIBITOR; 1.
PE   1: Evidence at protein level;
KW   3D-structure; Direct protein sequencing; Disulfide bond; Knottin;
KW   Protease inhibitor; Secreted; Serine protease inhibitor.
FT   PEPTIDE         1..32
FT                   /note="Trypsin inhibitor 3"
FT                   /id="PRO_0000033199"
FT   PEPTIDE         4..32
FT                   /note="Trypsin inhibitor 2"
FT                   /id="PRO_0000033200"
FT   SITE            8..9
FT                   /note="Reactive bond"
FT   DISULFID        6..23
FT                   /evidence="ECO:0000250"
FT   DISULFID        13..25
FT                   /evidence="ECO:0000250"
FT   DISULFID        19..31
FT                   /evidence="ECO:0000250"
FT   HELIX           16..18
FT                   /evidence="ECO:0007829|PDB:2BTC"
FT   STRAND          24..26
FT                   /evidence="ECO:0007829|PDB:2STB"
FT   STRAND          29..32
FT                   /evidence="ECO:0007829|PDB:2BTC"
SQ   SEQUENCE   32 AA;  3656 MW;  0F6B9820BA13D512 CRC64;
     HEERVCPKIL MECKKDSDCL AECICLEHGY CG