ID   TX214_APOSC             Reviewed;          76 AA.
AC   P49269;
DT   01-FEB-1996, integrated into UniProtKB/Swiss-Prot.
DT   01-FEB-1996, sequence version 1.
DT   25-MAY-2022, entry version 64.
DE   RecName: Full=U1-cyrtautoxin-As1b;
DE            Short=U1-CUTX-As1b;
DE   AltName: Full=Aptotoxin IV;
DE   AltName: Full=Aptotoxin-4;
DE   AltName: Full=Paralytic peptide IV;
DE            Short=PP IV;
OS   Apomastus schlingeri (Trap-door spider) (Aptostichus schlingeri).
OC   Eukaryota; Metazoa; Ecdysozoa; Arthropoda; Chelicerata; Arachnida; Araneae;
OC   Mygalomorphae; Euctenizidae; Apomastus.
OX   NCBI_TaxID=12944;
RN   [1]
RP   PROTEIN SEQUENCE, FUNCTION, TOXIC DOSE, SUBCELLULAR LOCATION, AND BIOASSAY.
RC   TISSUE=Venom;
RX   PubMed=1440641; DOI=10.1016/0041-0101(92)90049-b;
RA   Skinner W.S., Dennis P.A., Li J.P., Quistad G.B.;
RT   "Identification of insecticidal peptides from venom of the trap-door
RT   spider, Aptostichus schlingeri (Ctenizidae).";
RL   Toxicon 30:1043-1050(1992).
CC   -!- FUNCTION: Neurotoxin with probable ion channel impairing activity. Is
CC       both paralytic and lethal, when injected into lepidopteran larvae.
CC       {ECO:0000269|PubMed:1440641}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000269|PubMed:1440641}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland.
CC       {ECO:0000305|PubMed:1440641}.
CC   -!- DOMAIN: The presence of a 'disulfide through disulfide knot'
CC       structurally defines this protein as a knottin.
CC       {ECO:0000250|UniProtKB:A0A452CSQ9}.
CC   -!- TOXIC DOSE: LD(50) is 0.20 mg/kg by subcutaneous injection.
CC       {ECO:0000269|PubMed:1440641}.
CC   -!- SIMILARITY: Belongs to the neurotoxin 21 family. {ECO:0000305}.
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DR   PIR; D44007; D44007.
DR   AlphaFoldDB; P49269; -.
DR   SMR; P49269; -.
DR   ArachnoServer; AS000404; U1-cyrtautoxin-As1b.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0099106; F:ion channel regulator activity; IEA:UniProtKB-KW.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   InterPro; IPR035311; Cys_Knot_tox.
DR   Pfam; PF17486; Cys_Knot_tox; 1.
PE   1: Evidence at protein level;
KW   Direct protein sequencing; Disulfide bond; Ion channel impairing toxin;
KW   Knottin; Neurotoxin; Secreted; Toxin.
FT   CHAIN           1..76
FT                   /note="U1-cyrtautoxin-As1b"
FT                   /id="PRO_0000087664"
FT   DISULFID        23..37
FT                   /evidence="ECO:0000250|UniProtKB:A0A452CSQ9"
FT   DISULFID        30..51
FT                   /evidence="ECO:0000250|UniProtKB:A0A452CSQ9"
FT   DISULFID        36..66
FT                   /evidence="ECO:0000250|UniProtKB:A0A452CSQ9"
FT   DISULFID        69..76
FT                   /evidence="ECO:0000250|UniProtKB:A0A452CSQ9"
SQ   SEQUENCE   76 AA;  8342 MW;  2130A3A65B323AEF CRC64;
     EIPQNLGSGI PHDRIKLPNG QWCKTPGDLC SSSSECCKAK HSNSVTYASF CSREWSGQQG
     LFINQCRTCN VESSMC