ID   PA2B2_BUNMU             Reviewed;         145 AA.
AC   P00618; Q546H3;
DT   21-JUL-1986, integrated into UniProtKB/Swiss-Prot.
DT   01-NOV-1990, sequence version 2.
DT   02-SEP-2026, entry version 127.
DE   RecName: Full=Basic phospholipase A2 beta-bungarotoxin A2 chain;
DE            Short=Beta-BuTX A2 chain;
DE            Short=svPLA2;
DE            EC=3.1.1.4;
DE   AltName: Full=Phosphatidylcholine 2-acylhydrolase;
DE   Flags: Precursor;
OS   Bungarus multicinctus (Many-banded krait).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi;
OC   Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera;
OC   Serpentes; Colubroidea; Elapidae; Bungarinae; Bungarus.
OX   NCBI_TaxID=8616;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   TISSUE=Venom gland;
RX   PubMed=2388842; DOI=10.1093/nar/18.15.4609;
RA   Danse J.-M., Toussaint J.L., Kempf J.;
RT   "Nucleotide sequence encoding beta-bungarotoxin A2-chain from the venom
RT   glands of Bungarus multicinctus.";
RL   Nucleic Acids Res. 18:4609-4609(1990).
RN   [2] {ECO:0000312|EMBL:CAD24462.1}
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RC   TISSUE=Liver;
RX   PubMed=12368113; DOI=10.1016/s0041-0101(02)00160-5;
RA   Chu Y.P., Chang L.S.;
RT   "The organization of the genes encoding the A chains of beta-bungarotoxins:
RT   evidence for the skipping of exon.";
RL   Toxicon 40:1437-1443(2002).
RN   [3]
RP   PROTEIN SEQUENCE OF 26-145, SUBCELLULAR LOCATION, SUBUNIT, AND TOXIC DOSE.
RC   TISSUE=Venom;
RX   PubMed=7096305; DOI=10.1093/oxfordjournals.jbchem.a133844;
RA   Kondo K., Toda H., Narita K., Lee C.-Y.;
RT   "Amino acid sequences of three beta-bungarotoxins (beta 3-, beta 4-, and
RT   beta 5-bungarotoxins) from Bungarus multicinctus venom. Amino acid
RT   substitutions in the A chains.";
RL   J. Biochem. 91:1531-1548(1982).
RN   [4]
RP   REVIEW.
RX   PubMed=10936627; DOI=10.1016/s0041-0101(00)00159-8;
RA   Rowan E.G.;
RT   "What does beta-bungarotoxin do at the neuromuscular junction?";
RL   Toxicon 39:107-118(2001).
CC   -!- FUNCTION: Snake venom phospholipase A2 (PLA2) that inhibits
CC       neuromuscular transmission by blocking acetylcholine release from the
CC       nerve termini. PLA2 catalyzes the calcium-dependent hydrolysis of the
CC       2-acyl groups in 3-sn-phosphoglycerides.
CC   -!- CATALYTIC ACTIVITY:
CC       Reaction=a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1-acyl-sn-
CC         glycero-3-phosphocholine + a fatty acid + H(+); Xref=Rhea:RHEA:15801,
CC         ChEBI:CHEBI:15377, ChEBI:CHEBI:15378, ChEBI:CHEBI:28868,
CC         ChEBI:CHEBI:57643, ChEBI:CHEBI:58168; EC=3.1.1.4;
CC         Evidence={ECO:0000255|PROSITE-ProRule:PRU10035, ECO:0000255|PROSITE-
CC         ProRule:PRU10036};
CC   -!- COFACTOR:
CC       Name=Ca(2+); Xref=ChEBI:CHEBI:29108;
CC         Evidence={ECO:0000250|UniProtKB:P00617};
CC       Note=Binds 1 Ca(2+) ion. {ECO:0000250|UniProtKB:P00617};
CC   -!- SUBUNIT: Heterodimer; disulfide-linked. The A chains have phospholipase
CC       A2 activity and the B chains show homology with the basic protease
CC       inhibitors. The A2 chain is found in beta-3 and beta-4 bungarotoxins.
CC       {ECO:0000269|PubMed:7096305}.
CC   -!- SUBCELLULAR LOCATION: Secreted {ECO:0000269|PubMed:7096305}.
CC   -!- TISSUE SPECIFICITY: Expressed by the venom gland.
CC       {ECO:0000305|PubMed:7096305}.
CC   -!- TOXIC DOSE: LD(50) is 0.066 mg/kg by intraperitoneal injection into
CC       mice (beta-3 bungarotoxin). {ECO:0000269|PubMed:7096305}.
CC   -!- TOXIC DOSE: LD(50) is 0.072 mg/kg by intraperitoneal injection into
CC       mice (beta-4 bungarotoxin). {ECO:0000269|PubMed:7096305}.
CC   -!- SIMILARITY: Belongs to the phospholipase A2 family. Group I subfamily.
CC       D49 sub-subfamily. {ECO:0000305}.
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DR   EMBL; X53407; CAA37483.1; -; mRNA.
DR   EMBL; AJ431707; CAD24462.1; -; Genomic_DNA.
DR   PIR; S10980; PSKFA2.
DR   SMR; P00618; -.
DR   CDD; cd00125; PLA2c; 1.
DR   FunFam; 1.20.90.10:FF:000007; Acidic phospholipase A2; 1.
DR   Gene3D; 1.20.90.10; Phospholipase A2 domain; 1.
DR   InterPro; IPR001211; PLA2.
DR   InterPro; IPR016090; PLA2-like_dom.
DR   InterPro; IPR033112; PLA2_Asp_AS.
DR   InterPro; IPR033113; PLA2_histidine.
DR   InterPro; IPR036444; PLipase_A2_dom_sf.
DR   PANTHER; PTHR11716:SF100; PHOSPHOLIPASE A2; 1.
DR   PANTHER; PTHR11716; PHOSPHOLIPASE A2 FAMILY MEMBER; 1.
DR   Pfam; PF00068; Phospholip_A2_1; 1.
DR   PRINTS; PR00389; PHPHLIPASEA2.
DR   SMART; SM00085; PA2c; 1.
DR   SUPFAM; SSF48619; Phospholipase A2, PLA2; 1.
DR   PROSITE; PS00119; PA2_ASP; 1.
DR   PROSITE; PS00118; PA2_HIS; 1.
DR   GO; GO:0005576; C:extracellular region; EXP:UniProtKB.
DR   GO; GO:0004623; F:A2-type glycerophospholipase activity; IEA:UniProtKB-EC.
DR   GO; GO:0005509; F:calcium ion binding; IEA:InterPro.
DR   GO; GO:0005543; F:phospholipid binding; IEA:TreeGrafter.
DR   GO; GO:0050482; P:arachidonate secretion; IEA:InterPro.
DR   GO; GO:0016042; P:lipid catabolic process; IEA:InterPro.
DR   GO; GO:0006644; P:phospholipid metabolic process; IEA:InterPro.
DR   AlphaFoldDB; P00618; -.
PE   1: Evidence at protein level;
KW   Calcium; Direct protein sequencing; Disulfide bond; Hydrolase;
KW   Lipid degradation; Lipid metabolism; Metal-binding; Neurotoxin;
KW   Presynaptic neurotoxin; Secreted; Signal; Toxin.
FT   SIGNAL          1..17
FT                   /evidence="ECO:0000255"
FT   PROPEP          18..25
FT                   /evidence="ECO:0000305|PubMed:7096305"
FT                   /id="PRO_0000022837"
FT   CHAIN           26..145
FT                   /note="Basic phospholipase A2 beta-bungarotoxin A2 chain"
FT                   /evidence="ECO:0000269|PubMed:7096305"
FT                   /id="PRO_0000022838"
FT   ACT_SITE        73
FT                   /evidence="ECO:0000250|UniProtKB:P14418"
FT   ACT_SITE        119
FT                   /evidence="ECO:0000250|UniProtKB:P14418"
FT   BINDING         53
FT                   /ligand="Ca(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29108"
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   BINDING         55
FT                   /ligand="Ca(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29108"
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   BINDING         57
FT                   /ligand="Ca(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29108"
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   BINDING         74
FT                   /ligand="Ca(2+)"
FT                   /ligand_id="ChEBI:CHEBI:29108"
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   DISULFID        40
FT                   /note="Interchain (with a B chain)"
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   DISULFID        52..144
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   DISULFID        54..70
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   DISULFID        69..125
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   DISULFID        76..118
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   DISULFID        86..111
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   DISULFID        104..116
FT                   /evidence="ECO:0000250|UniProtKB:P00617"
FT   CONFLICT        91..92
FT                   /note="QS -> SQ (in Ref. 3; AA sequence)"
FT                   /evidence="ECO:0000305"
FT   CONFLICT        128
FT                   /note="N -> Q (in Ref. 3; AA sequence)"
FT                   /evidence="ECO:0000305"
FT   CONFLICT        130
FT                   /note="E -> D (in Ref. 3; AA sequence)"
FT                   /evidence="ECO:0000305"
SQ   SEQUENCE   145 AA;  16296 MW;  08CD9D0E84E57581 CRC64;
     MLIFLWCGAV CVSLLGAANI PPHPLNLINF MEMIRYTIPC EKTWGEYADY GCYCGAGGSG
     RPIDALDRCC YVHDNCYGDA EKKHKCNPKT QSYSYKLTKR TIICYGAAGT CARIVCDCDR
     TAALCFGNSE YIERHKNIDT KRHCR
//