ID   API3_ASCSU              Reviewed;         169 AA.
AC   P19400;
DT   01-NOV-1990, integrated into UniProtKB/Swiss-Prot.
DT   15-JUL-1999, sequence version 2.
DT   03-AUG-2022, entry version 96.
DE   RecName: Full=Major pepsin inhibitor 3;
DE            Short=PI-3;
DE   Flags: Precursor;
OS   Ascaris suum (Pig roundworm) (Ascaris lumbricoides).
OC   Eukaryota; Metazoa; Ecdysozoa; Nematoda; Chromadorea; Rhabditida;
OC   Spirurina; Ascaridomorpha; Ascaridoidea; Ascarididae; Ascaris.
OX   NCBI_TaxID=6253;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], AND CHARACTERIZATION.
RC   TISSUE=Body wall;
RX   PubMed=9654082; DOI=10.1046/j.1432-1327.1998.2530804.x;
RA   Kageyama T.;
RT   "Molecular cloning, expression and characterization of an Ascaris inhibitor
RT   for pepsin and cathepsin E.";
RL   Eur. J. Biochem. 253:804-809(1998).
RN   [2]
RP   PROTEIN SEQUENCE OF 21-169, PYROGLUTAMATE FORMATION AT GLN-21, AND
RP   DISULFIDE BONDS.
RX   PubMed=2223768; DOI=10.1021/bi00484a003;
RA   Martzen M.R., McMullen B.A., Smith N.E., Fujikawa K., Peanasky R.J.;
RT   "Primary structure of the major pepsin inhibitor from the intestinal
RT   parasitic nematode Ascaris suum.";
RL   Biochemistry 29:7366-7372(1990).
RN   [3]
RP   NUCLEOTIDE SEQUENCE [MRNA] OF 36-169.
RX   PubMed=9561246; DOI=10.1007/978-1-4615-5373-1_54;
RA   Zalatoris J., Rao-Naik C., Fecho G., Girdwood K., Kay J., Dunn B.M.;
RT   "Expression, purification, and characterization of the recombinant pepsin
RT   inhibitor from Ascaris suum.";
RL   Adv. Exp. Med. Biol. 436:387-389(1998).
RN   [4]
RP   X-RAY CRYSTALLOGRAPHY (1.75 ANGSTROMS) IN COMPLEX WITH PIG PEPSIN.
RX   PubMed=10932249; DOI=10.1038/77950;
RA   Ng K.K., Petersen J.F., Cherney M.M., Garen C., Zalatoris J.J.,
RA   Rao-Naik C., Dunn B.M., Martzen M.R., Peanasky R.J., James M.N.;
RT   "Structural basis for the inhibition of porcine pepsin by Ascaris pepsin
RT   inhibitor-3.";
RL   Nat. Struct. Biol. 7:653-657(2000).
CC   -!- FUNCTION: This is an inhibitor of the aspartic protease pepsin.
CC   -!- SUBCELLULAR LOCATION: Secreted.
CC   -!- TISSUE SPECIFICITY: Body wall.
CC   -!- SIMILARITY: Belongs to the protease inhibitor I33 family.
CC       {ECO:0000305}.
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DR   EMBL; AJ224688; CAA12072.1; -; mRNA.
DR   EMBL; U77034; AAB19209.1; -; mRNA.
DR   PDB; 1F32; X-ray; 1.75 A; A=21-169.
DR   PDB; 1F34; X-ray; 2.45 A; B=21-169.
DR   PDBsum; 1F32; -.
DR   PDBsum; 1F34; -.
DR   AlphaFoldDB; P19400; -.
DR   SMR; P19400; -.
DR   MINT; P19400; -.
DR   MEROPS; I33.001; -.
DR   EnsemblMetazoa; AgR017_g006_t01; AgR017_g006_t01; AgR017_g006.
DR   EvolutionaryTrace; P19400; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0019828; F:aspartic-type endopeptidase inhibitor activity; IEA:UniProtKB-KW.
DR   Gene3D; 3.30.1120.50; -; 2.
DR   InterPro; IPR010480; Pepsin-I3.
DR   InterPro; IPR038412; Pepsin-I3_sf.
DR   Pfam; PF06394; Pepsin-I3; 1.
PE   1: Evidence at protein level;
KW   3D-structure; Aspartic protease inhibitor; Direct protein sequencing;
KW   Disulfide bond; Protease inhibitor; Pyrrolidone carboxylic acid; Secreted;
KW   Signal.
FT   SIGNAL          1..20
FT                   /evidence="ECO:0000269|PubMed:2223768"
FT   CHAIN           21..169
FT                   /note="Major pepsin inhibitor 3"
FT                   /id="PRO_0000002394"
FT   REGION          135..169
FT                   /note="Disordered"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   COMPBIAS        154..169
FT                   /note="Pro residues"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   MOD_RES         21
FT                   /note="Pyrrolidone carboxylic acid"
FT                   /evidence="ECO:0000269|PubMed:2223768"
FT   DISULFID        33..79
FT                   /evidence="ECO:0000269|PubMed:2223768"
FT   DISULFID        68..86
FT                   /evidence="ECO:0000269|PubMed:2223768"
FT   DISULFID        99..166
FT                   /evidence="ECO:0000269|PubMed:2223768"
FT   STRAND          25..29
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   STRAND          33..36
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   STRAND          39..42
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   STRAND          45..49
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   HELIX           52..54
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   HELIX           55..70
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   HELIX           77..80
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   HELIX           84..86
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   STRAND          92..96
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   STRAND          99..102
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   STRAND          105..108
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   STRAND          111..115
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   HELIX           118..136
FT                   /evidence="ECO:0007829|PDB:1F32"
FT   HELIX           164..166
FT                   /evidence="ECO:0007829|PDB:1F32"
SQ   SEQUENCE   169 AA;  18657 MW;  1213BF2B8F5AFA8B CRC64;
     MHVWLILSLA SLWTSSIAYS QFLFSMSTGP FICTVKDNQV FVANLPWTML EGDDIQVGKE
     FAARVEDCTN VKHDMAPTCT KPPPFCGPQD MKMFNFVGCS VLGNKLFIDQ KYVRDLTAKD
     HAEVQTFREK IAAFEEQQEN QPPSSGMPHG AVPAGGLSPP PPPSFCTVQ