ID   3SDC1_OPHHA             Reviewed;          84 AA.
AC   Q2VBN5;
DT   15-JAN-2008, integrated into UniProtKB/Swiss-Prot.
DT   10-JAN-2006, sequence version 1.
DT   25-MAY-2022, entry version 62.
DE   RecName: Full=Beta-cardiotoxin CTX21;
DE   Flags: Precursor;
OS   Ophiophagus hannah (King cobra) (Naja hannah).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC   Serpentes; Colubroidea; Elapidae; Elapinae; Ophiophagus.
OX   NCBI_TaxID=8665;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   TISSUE=Venom gland;
RX   PubMed=16689684; DOI=10.1042/bj20060004;
RA   Li J., Zhang H., Liu J., Xu K.;
RT   "Novel genes encoding six kinds of three-finger toxins in Ophiophagus
RT   hannah (king cobra) and function characterization of two recombinant long-
RT   chain neurotoxins.";
RL   Biochem. J. 398:233-242(2006).
CC   -!- FUNCTION: Acts as a beta-blocker by binding to beta-1 and beta-2
CC       adrenergic receptors (ADRB1 and ADRB2). It dose-dependently decreases
CC       the heart rate (bradycardia), whereas conventional cardiotoxins
CC       increases it. At 100 mg/kg, intraperitoneal injection into mice
CC       provokes labored breathing, impaired locomotion, lack of response to
CC       external stimuli, and death (after 30 min).
CC       {ECO:0000250|UniProtKB:Q69CK0}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000250|UniProtKB:Q69CK0}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland. {ECO:0000305}.
CC   -!- MISCELLANEOUS: Does not affect blood coagulation and does not show
CC       significant hemolytic activity. {ECO:0000250|UniProtKB:Q69CK0}.
CC   -!- MISCELLANEOUS: Is classified as a P-type cytotoxin, since a proline
CC       residue stands at position 52 (Pro-31 in standard classification).
CC       {ECO:0000305}.
CC   -!- SIMILARITY: Belongs to the snake three-finger toxin family. Short-chain
CC       subfamily. Aminergic toxin sub-subfamily. {ECO:0000305}.
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DR   EMBL; DQ273580; ABB83634.1; -; mRNA.
DR   AlphaFoldDB; Q2VBN5; -.
DR   SMR; Q2VBN5; -.
DR   GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR   GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR   CDD; cd00206; snake_toxin; 1.
DR   Gene3D; 2.10.60.10; -; 1.
DR   InterPro; IPR003572; Cytotoxin_Cobra.
DR   InterPro; IPR016054; LY6_UPA_recep-like.
DR   InterPro; IPR003571; Snake_3FTx.
DR   InterPro; IPR045860; Snake_toxin-like_sf.
DR   InterPro; IPR018354; Snake_toxin_con_site.
DR   Pfam; PF00021; UPAR_LY6; 1.
DR   PRINTS; PR00282; CYTOTOXIN.
DR   SUPFAM; SSF57302; SSF57302; 1.
DR   PROSITE; PS00272; SNAKE_TOXIN; 1.
PE   3: Inferred from homology;
KW   Cardiotoxin; Disulfide bond; G-protein coupled receptor impairing toxin;
KW   Secreted; Signal; Toxin.
FT   SIGNAL          1..21
FT                   /evidence="ECO:0000250|UniProtKB:Q69CK0"
FT   CHAIN           22..84
FT                   /note="Beta-cardiotoxin CTX21"
FT                   /id="PRO_5000006490"
FT   DISULFID        24..43
FT                   /evidence="ECO:0000250|UniProtKB:Q69CK0"
FT   DISULFID        36..61
FT                   /evidence="ECO:0000250|UniProtKB:Q69CK0"
FT   DISULFID        65..76
FT                   /evidence="ECO:0000250|UniProtKB:Q69CK0"
FT   DISULFID        77..82
FT                   /evidence="ECO:0000250|UniProtKB:Q69CK0"
SQ   SEQUENCE   84 AA;  9255 MW;  8A59407FCDDD655F CRC64;
     MKTLLLTLVV VTIVCLDLGY TRKCLNTPLP LIYTTCPIGQ DKCVKMTIKK LPSKYDVIRG
     CTDICPKSSA DVVVVCCDTN KCNK