ID   CAS1_CONST              Reviewed;          64 AA.
AC   P15471;
DT   01-APR-1990, integrated into UniProtKB/Swiss-Prot.
DT   11-JUL-2002, sequence version 2.
DT   25-MAY-2022, entry version 91.
DE   RecName: Full=Alpha-conotoxin SI {ECO:0000303|PubMed:10573284, ECO:0000303|PubMed:10913630, ECO:0000303|PubMed:14701840, ECO:0000303|PubMed:3196703};
DE   Flags: Precursor;
OS   Conus striatus (Striated cone).
OC   Eukaryota; Metazoa; Spiralia; Lophotrochozoa; Mollusca; Gastropoda;
OC   Caenogastropoda; Neogastropoda; Conoidea; Conidae; Conus; Pionoconus.
OX   NCBI_TaxID=6493;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   TISSUE=Venom duct;
RX   PubMed=10573284; DOI=10.1016/s0196-9781(99)00116-3;
RA   Lu B.-S., Yu F., Zhao D., Huang P.-T., Huang C.-F.;
RT   "Conopeptides from Conus striatus and Conus textile by cDNA cloning.";
RL   Peptides 20:1139-1144(1999).
RN   [2]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   TISSUE=Venom duct;
RX   PubMed=14701840; DOI=10.1074/jbc.m309654200;
RA   Santos A.D., McIntosh J.M., Hillyard D.R., Cruz L.J., Olivera B.M.;
RT   "The A-superfamily of conotoxins: structural and functional divergence.";
RL   J. Biol. Chem. 279:17596-17606(2004).
RN   [3]
RP   PROTEIN SEQUENCE OF 50-62, AND SUBCELLULAR LOCATION.
RC   TISSUE=Venom;
RX   PubMed=3196703; DOI=10.1021/bi00418a065;
RA   Zafaralla G.C., Ramilo C., Gray W.R., Karlstroem R., Olivera B.M.,
RA   Cruz L.J.;
RT   "Phylogenetic specificity of cholinergic ligands: alpha-conotoxin SI.";
RL   Biochemistry 27:7102-7105(1988).
RN   [4]
RP   STRUCTURE BY NMR OF 50-62, DISULFIDE BONDS, AND AMIDATION AT CYS-62.
RX   PubMed=10913630; DOI=10.1016/s0014-5793(00)01724-5;
RA   Benie A.J., Whitford D., Hargittai B., Barany G., Janes R.W.;
RT   "Solution structure of alpha-conotoxin SI.";
RL   FEBS Lett. 476:287-295(2000).
CC   -!- FUNCTION: Alpha-conotoxins act on postsynaptic membranes, they bind to
CC       the nicotinic acetylcholine receptors (nAChR) and thus inhibit them.
CC       This toxin blocks muscular nAChRs alpha-1/gamma and alpha-1/delta
CC       subunits.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000269|PubMed:3196703}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom duct.
CC       {ECO:0000305|PubMed:3196703}.
CC   -!- DOMAIN: The cysteine framework is I (CC-C-C). Alpha3/5 pattern.
CC   -!- SIMILARITY: Belongs to the conotoxin A superfamily. {ECO:0000305}.
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DR   PIR; A28953; A28953.
DR   PDB; 1HJE; X-ray; 0.75 A; A=50-62.
DR   PDB; 1QMW; NMR; -; A=50-62.
DR   PDBsum; 1HJE; -.
DR   PDBsum; 1QMW; -.
DR   AlphaFoldDB; P15471; -.
DR   SMR; P15471; -.
DR   ConoServer; 76; SI precursor.
DR   EvolutionaryTrace; P15471; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0035792; C:host cell postsynaptic membrane; IEA:UniProtKB-KW.
DR   GO; GO:0030550; F:acetylcholine receptor inhibitor activity; IEA:UniProtKB-KW.
DR   GO; GO:0099106; F:ion channel regulator activity; IEA:UniProtKB-KW.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   InterPro; IPR009958; Conotoxin_a-typ.
DR   InterPro; IPR018072; Conotoxin_a-typ_CS.
DR   Pfam; PF07365; Toxin_8; 1.
DR   PROSITE; PS60014; ALPHA_CONOTOXIN; 1.
PE   1: Evidence at protein level;
KW   3D-structure; Acetylcholine receptor inhibiting toxin; Amidation;
KW   Direct protein sequencing; Disulfide bond; Ion channel impairing toxin;
KW   Neurotoxin; Postsynaptic neurotoxin; Secreted; Signal; Toxin.
FT   SIGNAL          1..21
FT                   /evidence="ECO:0000255"
FT   PROPEP          22..49
FT                   /evidence="ECO:0000305|PubMed:3196703"
FT                   /id="PRO_0000034887"
FT   PEPTIDE         50..62
FT                   /note="Alpha-conotoxin SI"
FT                   /evidence="ECO:0000269|PubMed:10913630"
FT                   /id="PRO_0000034888"
FT   REGION          23..47
FT                   /note="Disordered"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   COMPBIAS        26..47
FT                   /note="Basic and acidic residues"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   MOD_RES         62
FT                   /note="Cysteine amide"
FT                   /evidence="ECO:0000269|PubMed:10913630"
FT   DISULFID        51..56
FT                   /evidence="ECO:0000269|PubMed:10913630,
FT                   ECO:0007744|PDB:1HJE, ECO:0007744|PDB:1QMW"
FT   DISULFID        52..62
FT                   /evidence="ECO:0000269|PubMed:10913630,
FT                   ECO:0007744|PDB:1HJE, ECO:0007744|PDB:1QMW"
FT   HELIX           54..59
FT                   /evidence="ECO:0007829|PDB:1HJE"
SQ   SEQUENCE   64 AA;  7164 MW;  B104B80CCD7C3B41 CRC64;
     MGMRMMFTVF LLVVLATTVV SFPSDRASDG RDDEAKDERS DMHESDRKEI CCNPACGPKY
     SCGR