ID   CYT_CRYNI               Reviewed;         141 AA.
AC   E3P6P1;
DT   24-JUL-2013, integrated into UniProtKB/Swiss-Prot.
DT   11-JAN-2011, sequence version 1.
DT   25-MAY-2022, entry version 25.
DE   RecName: Full=Cystatin;
DE   Flags: Precursor;
OS   Cryptophis nigrescens (Eastern small-eyed snake) (Rhinoplocephalus
OS   nigrescens).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC   Serpentes; Colubroidea; Elapidae; Cryptophis.
OX   NCBI_TaxID=292442;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], AND LEVEL OF PROTEIN EXPRESSION.
RC   TISSUE=Venom, and Venom gland;
RX   PubMed=21172403; DOI=10.1016/j.biochi.2010.12.008;
RA   Richards R., St Pierre L., Trabi M., Johnson L.A., de Jersey J.,
RA   Masci P.P., Lavin M.F.;
RT   "Cloning and characterisation of novel cystatins from elapid snake venom
RT   glands.";
RL   Biochimie 93:659-668(2011).
CC   -!- FUNCTION: Inhibits various C1 cysteine proteases including cathepsin L,
CC       papain and cathepsin B. This protein has no toxic activity and its
CC       function in the venom is unknown. It may play a role as a housekeeping
CC       or regulatory protein (By similarity). {ECO:0000250}.
CC   -!- SUBCELLULAR LOCATION: Secreted.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland at an extremely low
CC       level (at protein level). {ECO:0000305|PubMed:21172403}.
CC   -!- MISCELLANEOUS: The recombinant protein does not inhibit calpain-1
CC       (CAPN1), a C2 family cysteine protease and legumain (LGMN), a C13
CC       family cysteine protease. Does not provoke cell death (PC3 prostate
CC       cancer cells) (By similarity). {ECO:0000250}.
CC   -!- SIMILARITY: Belongs to the cystatin family. {ECO:0000305}.
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DR   EMBL; FJ411286; ACR83847.1; -; mRNA.
DR   AlphaFoldDB; E3P6P1; -.
DR   SMR; E3P6P1; -.
DR   MEROPS; I25.012; -.
DR   GO; GO:0005576; C:extracellular region; 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   InterPro; IPR018073; Prot_inh_cystat_CS.
DR   Pfam; PF00031; Cystatin; 1.
DR   SMART; SM00043; CY; 1.
DR   SUPFAM; SSF54403; SSF54403; 1.
DR   PROSITE; PS00287; CYSTATIN; 1.
PE   1: Evidence at protein level;
KW   Disulfide bond; Protease inhibitor; Secreted; Signal;
KW   Thiol protease inhibitor.
FT   SIGNAL          1..26
FT                   /evidence="ECO:0000250"
FT   CHAIN           27..141
FT                   /note="Cystatin"
FT                   /id="PRO_5000654425"
FT   DOMAIN          29..129
FT                   /note="Cystatin"
FT   MOTIF           73..77
FT                   /note="Secondary area of contact"
FT                   /evidence="ECO:0000250"
FT   SITE            29
FT                   /note="Reactive site"
FT                   /evidence="ECO:0000250"
FT   DISULFID        91..107
FT                   /evidence="ECO:0000250"
FT   DISULFID        120..140
FT                   /evidence="ECO:0000250"
SQ   SEQUENCE   141 AA;  15858 MW;  A8C62CB4A891A4D6 CRC64;
     MVHSQLPVAA SLRLLCALLL LPSATMIPGG LSPRSVTDPD VREAAEFAVQ EYNALSANAY
     YYKQLRIVEA QSQVVAGAKY YLTMELMKTK CAKTTGKPKV YKEIQNCELP PKAQQEKLTC
     RFQVWSRPWL KKTELTKMSC N