ID   I2B_CONBE               Reviewed;          70 AA.
AC   Q9U3Z3;
DT   23-JAN-2002, integrated into UniProtKB/Swiss-Prot.
DT   01-MAY-2000, sequence version 1.
DT   25-MAY-2022, entry version 80.
DE   RecName: Full=Kappa-conotoxin BtX {ECO:0000303|PubMed:12547831};
DE   AltName: Full=BeTx {ECO:0000312|EMBL:AAF23167.1};
DE   Flags: Precursor;
OS   Conus betulinus (Beech cone).
OC   Eukaryota; Metazoa; Spiralia; Lophotrochozoa; Mollusca; Gastropoda;
OC   Caenogastropoda; Neogastropoda; Conoidea; Conidae; Conus; Dendroconus.
OX   NCBI_TaxID=89764;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA], PROTEIN SEQUENCE OF 27-43, FUNCTION, MASS
RP   SPECTROMETRY, HYDROXYLATION AT PRO-53, GAMMA-CARBOXYGLUTAMATION AT GLU-30;
RP   GLU-35 AND GLU-44, AMIDATION AT PRO-57, AND SUBCELLULAR LOCATION.
RC   TISSUE=Venom, and Venom duct;
RX   PubMed=12547831; DOI=10.1074/jbc.m210200200;
RA   Fan C.-X., Chen X.-K., Zhang C., Wang L.-X., Duan K.-L., He L.-L., Cao Y.,
RA   Liu S.-Y., Zhong M.-N., Ulens C., Tytgat J., Chen J.-S., Chi C.-W.,
RA   Zhou Z.;
RT   "A novel conotoxin from Conus betulinus, kappa-BtX, unique in cysteine
RT   pattern and in function as a specific BK channel modulator.";
RL   J. Biol. Chem. 278:12624-12633(2003).
CC   -!- FUNCTION: Modulator of potassium channels, specifically up-modulates
CC       the calcium and voltage-gated BK channels, has no effect on single
CC       channel conductance, but increases the open probability of BK channels.
CC       {ECO:0000269|PubMed:12547831}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000269|PubMed:12547831}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom duct.
CC       {ECO:0000305|PubMed:12547831}.
CC   -!- DOMAIN: The cysteine framework is XI (C-C-CC-CC-C-C). {ECO:0000305}.
CC   -!- PTM: Contains 4 disulfide bonds. {ECO:0000269|PubMed:12547831}.
CC   -!- MASS SPECTROMETRY: Mass=3569; Method=Electrospray;
CC       Evidence={ECO:0000269|PubMed:12547831};
CC   -!- SIMILARITY: Belongs to the conotoxin I2 superfamily. {ECO:0000305}.
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DR   EMBL; AF208661; AAF23167.1; -; mRNA.
DR   AlphaFoldDB; Q9U3Z3; -.
DR   SMR; Q9U3Z3; -.
DR   TCDB; 8.B.21.1.9; the spider insecticidal neurotoxin cyrtautoxin (cyrautoxin) family.
DR   ConoServer; 1106; BtX precursor.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0015459; F:potassium channel regulator activity; IEA:UniProtKB-KW.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   InterPro; IPR013141; Conotoxin-I_CS.
DR   InterPro; IPR020242; Conotoxin_I2-superfamily.
DR   Pfam; PF17557; Conotoxin_I2; 1.
DR   PROSITE; PS60019; I_CONOTOXIN; 1.
PE   1: Evidence at protein level;
KW   Amidation; Cleavage on pair of basic residues; Direct protein sequencing;
KW   Disulfide bond; Gamma-carboxyglutamic acid; Hydroxylation;
KW   Ion channel impairing toxin; Neurotoxin; Potassium channel impairing toxin;
KW   Secreted; Signal; Toxin.
FT   SIGNAL          1..26
FT                   /evidence="ECO:0000269|PubMed:12547831"
FT   PEPTIDE         27..57
FT                   /note="Kappa-conotoxin BtX"
FT                   /id="PRO_0000035086"
FT   PROPEP          61..70
FT                   /id="PRO_0000035087"
FT   MOD_RES         30
FT                   /note="4-carboxyglutamate"
FT                   /evidence="ECO:0000269|PubMed:12547831"
FT   MOD_RES         35
FT                   /note="4-carboxyglutamate"
FT                   /evidence="ECO:0000269|PubMed:12547831"
FT   MOD_RES         44
FT                   /note="4-carboxyglutamate"
FT                   /evidence="ECO:0000269|PubMed:12547831"
FT   MOD_RES         53
FT                   /note="4-hydroxyproline"
FT                   /evidence="ECO:0000269|PubMed:12547831"
FT   MOD_RES         57
FT                   /note="Proline amide"
FT                   /evidence="ECO:0000269|PubMed:12547831"
FT   DISULFID        27..41
FT                   /evidence="ECO:0000250|UniProtKB:Q7Z094"
FT   DISULFID        34..46
FT                   /evidence="ECO:0000250|UniProtKB:Q7Z094"
FT   DISULFID        40..50
FT                   /evidence="ECO:0000250|UniProtKB:Q7Z094"
FT   DISULFID        45..54
FT                   /evidence="ECO:0000250|UniProtKB:Q7Z094"
SQ   SEQUENCE   70 AA;  7900 MW;  F6575A2E830AD903 CRC64;
     MMFRVTSVGC LLLVIVFLNL VVPTSACRAE GTYCENDSQC CLNECCWGGC GHPCRHPGKR
     SKLQEFFRQR