ID   CYT_CYACP               Reviewed;         131 AA.
AC   Q331K1;
DT   24-JUL-2013, integrated into UniProtKB/Swiss-Prot.
DT   06-DEC-2005, sequence version 1.
DT   25-MAY-2022, entry version 39.
DE   RecName: Full=Cystatin J;
DE   Flags: Precursor;
OS   Cyanea capillata (Lion's mane jellyfish) (Cyanea arctica).
OC   Eukaryota; Metazoa; Cnidaria; Scyphozoa; Semaeostomeae; Cyaneidae; Cyanea.
OX   NCBI_TaxID=27804;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], AND FUNCTION.
RC   TISSUE=Tentacle;
RX   PubMed=14644559; DOI=10.1016/s0300-9084(03)00132-9;
RA   Yang Y., Cun S., Peng L., Xie X., Wei J., Yang W., Xu A.;
RT   "cDNA cloning, identification and characterization of a novel cystatin from
RT   the tentacle of Cyanea capillata.";
RL   Biochimie 85:1033-1039(2003).
CC   -!- FUNCTION: This recombinant protein inhibits the C1 cysteine protease
CC       papain (Ki is below 0.5 nM). {ECO:0000269|PubMed:14644559}.
CC   -!- SUBCELLULAR LOCATION: Secreted. Nematocyst {ECO:0000250}.
CC   -!- MISCELLANEOUS: Activity of this protein is stable at pH 4-11 at 4
CC       degrees Celsius, but unstable at neutral pH at >50 degrees Celsius.
CC       {ECO:0000305|PubMed:14644559}.
CC   -!- SIMILARITY: Belongs to the cystatin family. {ECO:0000305}.
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DR   EMBL; AY167572; AAO38706.1; -; mRNA.
DR   AlphaFoldDB; Q331K1; -.
DR   SMR; Q331K1; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0042151; C:nematocyst; IEA:UniProtKB-SubCell.
DR   GO; GO:0004869; F:cysteine-type endopeptidase inhibitor activity; IEA:UniProtKB-KW.
DR   CDD; cd00042; CY; 1.
DR   InterPro; IPR000010; Cystatin_dom.
DR   InterPro; IPR046350; Cystatin_sf.
DR   Pfam; PF00031; Cystatin; 1.
DR   SMART; SM00043; CY; 1.
DR   SUPFAM; SSF54403; SSF54403; 1.
PE   2: Evidence at transcript level;
KW   Disulfide bond; Nematocyst; Protease inhibitor; Secreted; Signal;
KW   Thiol protease inhibitor.
FT   SIGNAL          1..18
FT                   /evidence="ECO:0000255"
FT   CHAIN           19..131
FT                   /note="Cystatin J"
FT                   /id="PRO_0000423037"
FT   DOMAIN          35..109
FT                   /note="Cystatin"
FT   MOTIF           68..72
FT                   /note="Secondary area of contact"
FT                   /evidence="ECO:0000250"
FT   SITE            22
FT                   /note="Reactive site"
FT                   /evidence="ECO:0000250"
FT   DISULFID        86..97
FT                   /evidence="ECO:0000250"
FT   DISULFID        107..128
FT                   /evidence="ECO:0000250"
SQ   SEQUENCE   131 AA;  14739 MW;  1A15FA14583D29A1 CRC64;
     MHLYLCVLVC LSIGMANCLL PGGIRRMTDE EIQNDEILLT GVEFAVDKYN SDTNSRLIAT
     NVISATVQVV AGFKYNALIE LRPRLCVQDP KTKIATCPLR MNLPTKCSFT FLYQSWVPQK
     YSMLSTKCLR A