ID   IPRB_SAGSA              Reviewed;         181 AA.
AC   P07479;
DT   01-APR-1988, integrated into UniProtKB/Swiss-Prot.
DT   01-JUL-1993, sequence version 2.
DT   25-MAY-2022, entry version 85.
DE   RecName: Full=Proteinase inhibitor B;
DE   AltName: Full=Double-headed proteinase inhibitor B;
DE            Short=API-B;
DE   Flags: Precursor;
OS   Sagittaria sagittifolia (Arrowhead).
OC   Eukaryota; Viridiplantae; Streptophyta; Embryophyta; Tracheophyta;
OC   Spermatophyta; Magnoliopsida; Liliopsida; Alismataceae; Sagittaria.
OX   NCBI_TaxID=4451;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RX   PubMed=8468321; DOI=10.1093/oxfordjournals.jbchem.a124019;
RA   Xu W., Tao W., Gong Z., Chi C.-W.;
RT   "cDNA and genomic structures of arrowhead proteinase inhibitors.";
RL   J. Biochem. 113:153-158(1993).
RN   [2]
RP   PROTEIN SEQUENCE OF 25-174.
RX   PubMed=1618743; DOI=10.1093/oxfordjournals.jbchem.a123792;
RA   Yang H.-L., Luo R.-S., Wang L.-X., Zhu D.-X., Chi C.-W.;
RT   "Primary structure and disulfide bridge location of arrowhead double-headed
RT   proteinase inhibitors.";
RL   J. Biochem. 111:537-545(1992).
RN   [3]
RP   PRELIMINARY PROTEIN SEQUENCE OF 25-174.
RC   TISSUE=Root;
RX   PubMed=3907662; DOI=10.1515/bchm3.1985.366.2.879;
RA   Chi C.-W., Zhu D.-X., Lin N.-Q., Xu L.-X., Tan F.-L., Wang L.-X.;
RT   "The complete amino-acid sequence of the proteinase inhibitor B from the
RT   root of the arrowhead (Sagittaria sagittifolia L.).";
RL   Biol. Chem. Hoppe-Seyler 366:879-885(1985).
RN   [4]
RP   PRELIMINARY PROTEIN SEQUENCE OF 25-174.
RC   TISSUE=Root;
RA   Chi C.-W., Zhu D.-X., Lin N.-Q., Xu L.-X., Tan F.-L., Wang L.-X.;
RT   "The complete amino-acid sequence of the arrowhead proteinase inhibitor
RT   B.";
RL   Sheng Wu Hua Xue Yu Sheng Wu Wu Li Xue Bao 18:156-163(1986).
CC   -!- FUNCTION: Possesses two reactive sites. Inhibits two molecules of
CC       trypsin simultaneously. Inhibits efficiently kallikrein, but
CC       chymotrypsin weakly.
CC   -!- SUBCELLULAR LOCATION: Secreted.
CC   -!- SIMILARITY: Belongs to the protease inhibitor I3 (leguminous Kunitz-
CC       type inhibitor) family. {ECO:0000305}.
CC   -!- SEQUENCE CAUTION:
CC       Sequence=Ref.2; Type=Miscellaneous discrepancy; Note=Very different preliminary sequence.; Evidence={ECO:0000305};
CC       Sequence=Ref.3; Type=Miscellaneous discrepancy; Note=Very different preliminary sequence.; Evidence={ECO:0000305};
CC       Sequence=Ref.4; Type=Miscellaneous discrepancy; Note=Very different preliminary sequence.; Evidence={ECO:0000305};
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DR   EMBL; D13820; BAA02973.1; -; Genomic_DNA.
DR   PIR; JX0247; JX0247.
DR   AlphaFoldDB; P07479; -.
DR   SMR; P07479; -.
DR   MEROPS; I03.007; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0004867; F:serine-type endopeptidase inhibitor activity; IEA:UniProtKB-KW.
DR   InterPro; IPR011065; Kunitz_inhibitor_STI-like_sf.
DR   InterPro; IPR016308; Prot_inh_API-A/B.
DR   InterPro; IPR002160; Prot_inh_Kunz-lg.
DR   PANTHER; PTHR33107; PTHR33107; 2.
DR   Pfam; PF00197; Kunitz_legume; 1.
DR   PIRSF; PIRSF001653; API-B; 1.
DR   SMART; SM00452; STI; 1.
DR   SUPFAM; SSF50386; SSF50386; 1.
PE   1: Evidence at protein level;
KW   Direct protein sequencing; Disulfide bond; Protease inhibitor; Secreted;
KW   Serine protease inhibitor; Signal.
FT   SIGNAL          1..24
FT                   /evidence="ECO:0000269|PubMed:1618743"
FT   CHAIN           25..181
FT                   /note="Proteinase inhibitor B"
FT                   /id="PRO_0000016898"
FT   SITE            68..69
FT                   /note="Reactive bond for trypsin"
FT                   /evidence="ECO:0000305"
FT   SITE            100..101
FT                   /note="Reactive bond"
FT                   /evidence="ECO:0000305"
FT   DISULFID        67..113
FT   DISULFID        134..143
FT   DISULFID        136..139
FT   CONFLICT        61
FT                   /note="T -> A (in Ref. 2; AA sequence)"
FT                   /evidence="ECO:0000305"
FT   CONFLICT        152
FT                   /note="N -> D (in Ref. 2; AA sequence)"
FT                   /evidence="ECO:0000305"
FT   CONFLICT        171
FT                   /note="S -> F (in Ref. 2; AA sequence)"
FT                   /evidence="ECO:0000305"
SQ   SEQUENCE   181 AA;  19174 MW;  D21AB5C7BB3412DF CRC64;
     MAASNALLLI SGALLISLAV LCQGDPVVDS DGDAVQLNLG GRYPLYTIES AAIGFHGGLS
     TLHKDVCKSY VYEAPETDRG LPVSFSASAT SEPVMQLGSR YKFSFLMPVP RICDTAWSVG
     KSTEETGVYK LAACSCEFCK IACPEVGSFN VNGKTLLGIG GEHFTVRFHK SDALAMKTAP
     Q