IPTXI_PANIM
ID IPTXI_PANIM Reviewed; 167 AA.
AC P59888;
DT 26-SEP-2003, integrated into UniProtKB/Swiss-Prot.
DT 26-SEP-2003, sequence version 1.
DT 03-AUG-2022, entry version 85.
DE RecName: Full=Phospholipase A2 imperatoxin-1;
DE AltName: Full=Imperatoxin I;
DE Short=IpTx1;
DE Short=IpTxi;
DE AltName: Full=Imperatoxin inhibitor;
DE Contains:
DE RecName: Full=Imperatoxin-1 large subunit;
DE EC=3.1.1.4;
DE AltName: Full=Imperatoxin I large subunit;
DE Contains:
DE RecName: Full=Imperatoxin-1 small subunit;
DE AltName: Full=Imperatoxin I small subunit;
DE Flags: Precursor;
OS Pandinus imperator (Emperor scorpion).
OC Eukaryota; Metazoa; Ecdysozoa; Arthropoda; Chelicerata; Arachnida;
OC Scorpiones; Iurida; Scorpionoidea; Scorpionidae; Pandininae; Pandinus.
OX NCBI_TaxID=55084;
RN [1]
RP NUCLEOTIDE SEQUENCE [MRNA], PROTEIN SEQUENCE OF 32-135 AND 141-167,
RP SUBUNIT, FUNCTION, AND MUTAGENESIS OF CYS-144.
RC TISSUE=Venom, and Venom gland;
RX PubMed=9115249; DOI=10.1074/jbc.272.18.11886;
RA Zamudio F.Z., Conde R., Arevalo C., Becerril B., Martin B.M.,
RA Valdivia H.H., Possani L.D.;
RT "The mechanism of inhibition of ryanodine receptor channels by imperatoxin
RT I, a heterodimeric protein from the scorpion Pandinus imperator.";
RL J. Biol. Chem. 272:11886-11894(1997).
RN [2]
RP IDENTIFICATION.
RX PubMed=1334561; DOI=10.1073/pnas.89.24.12185;
RA Valdivia H.H., Kirby M.S., Lederer W.J., Coronado R.;
RT "Scorpion toxins targeted against the sarcoplasmic reticulum Ca(2+)-release
RT channel of skeletal and cardiac muscle.";
RL Proc. Natl. Acad. Sci. U.S.A. 89:12185-12189(1992).
CC -!- FUNCTION: Phospholipase toxin, which may catalyze the calcium-dependent
CC hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides. Inhibits
CC both skeletal (RYR1) and cardiac (RYR2) ryanodine receptors (calcium
CC release channels). Probably blocks ryanodine receptors by generating a
CC lipid product. {ECO:0000269|PubMed:9115249}.
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};
CC -!- COFACTOR:
CC Name=Ca(2+); Xref=ChEBI:CHEBI:29108; Evidence={ECO:0000250};
CC Note=Binds 1 Ca(2+) ion. {ECO:0000250};
CC -!- SUBUNIT: Heterodimer composed of a large subunit and a small subunit;
CC disulfide-linked. {ECO:0000269|PubMed:9115249}.
CC -!- SUBCELLULAR LOCATION: Secreted.
CC -!- TISSUE SPECIFICITY: Expressed by the venom gland.
CC -!- SIMILARITY: Belongs to the phospholipase A2 family. Group III
CC subfamily. {ECO:0000305}.
CC -!- CAUTION: In contrast to other phospholipases, it lacks the typical Asp
CC active site (Asp->Glu in position 93). {ECO:0000305}.
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DR AlphaFoldDB; P59888; -.
DR SMR; P59888; -.
DR PRIDE; P59888; -.
DR GO; GO:0005576; C:extracellular region; IEA:UniProtKB-SubCell.
DR GO; GO:0005246; F:calcium channel regulator activity; IEA:UniProtKB-KW.
DR GO; GO:0046872; F:metal ion binding; IEA:UniProtKB-KW.
DR GO; GO:0004623; F:phospholipase A2 activity; IEA:UniProtKB-EC.
DR GO; GO:0090729; F:toxin activity; IEA:UniProtKB-KW.
DR GO; GO:0050482; P:arachidonic acid secretion; IEA:InterPro.
DR GO; GO:0016042; P:lipid catabolic process; IEA:UniProtKB-KW.
DR GO; GO:0006644; P:phospholipid metabolic process; IEA:InterPro.
DR Gene3D; 1.20.90.10; -; 1.
DR InterPro; IPR016090; PLipase_A2_dom.
DR InterPro; IPR036444; PLipase_A2_dom_sf.
DR InterPro; IPR033113; PLipase_A2_His_AS.
DR Pfam; PF05826; Phospholip_A2_2; 1.
DR SUPFAM; SSF48619; SSF48619; 1.
DR PROSITE; PS00118; PA2_HIS; 1.
PE 1: Evidence at protein level;
KW Calcium; Calcium channel impairing toxin; Direct protein sequencing;
KW Disulfide bond; Glycoprotein; Hydrolase; Ion channel impairing toxin;
KW Lipid degradation; Lipid metabolism; Metal-binding; Neurotoxin;
KW Ryanodine-sensitive calcium-release channel impairing toxin; Secreted;
KW Signal; Toxin; Zymogen.
FT SIGNAL 1..?
FT /evidence="ECO:0000255"
FT PROPEP ?..31
FT /evidence="ECO:0000255"
FT /id="PRO_0000022988"
FT CHAIN 32..135
FT /note="Imperatoxin-1 large subunit"
FT /id="PRO_0000022989"
FT PROPEP 136..140
FT /evidence="ECO:0000269|PubMed:9115249"
FT /id="PRO_0000022990"
FT CHAIN 141..167
FT /note="Imperatoxin-1 small subunit"
FT /id="PRO_0000022991"
FT ACT_SITE 64
FT /evidence="ECO:0000255|PROSITE-ProRule:PRU10035"
FT BINDING 38
FT /ligand="Ca(2+)"
FT /ligand_id="ChEBI:CHEBI:29108"
FT /evidence="ECO:0000250|UniProtKB:P00630"
FT BINDING 40
FT /ligand="Ca(2+)"
FT /ligand_id="ChEBI:CHEBI:29108"
FT /evidence="ECO:0000250|UniProtKB:P00630"
FT BINDING 42
FT /ligand="Ca(2+)"
FT /ligand_id="ChEBI:CHEBI:29108"
FT /evidence="ECO:0000250|UniProtKB:P00630"
FT BINDING 65
FT /ligand="Ca(2+)"
FT /ligand_id="ChEBI:CHEBI:29108"
FT /evidence="ECO:0000250|UniProtKB:P00630"
FT CARBOHYD 102
FT /note="N-linked (GlcNAc...) asparagine"
FT /evidence="ECO:0000255"
FT DISULFID 39..61
FT /evidence="ECO:0000250|UniProtKB:Q6T178"
FT DISULFID 60..99
FT /evidence="ECO:0000250|UniProtKB:Q6T178"
FT DISULFID 67..92
FT /evidence="ECO:0000250|UniProtKB:Q6T178"
FT DISULFID 90..127
FT /evidence="ECO:0000250|UniProtKB:Q6T178"
FT DISULFID 132..144
FT /note="Interchain (between large and small subunits)"
FT /evidence="ECO:0000250|UniProtKB:Q6T178"
FT MUTAGEN 144
FT /note="C->M,A: Does not affect the binding of ryanodine to
FT cardiac ryanodine receptor."
FT /evidence="ECO:0000269|PubMed:9115249"
SQ SEQUENCE 167 AA; 18664 MW; 027420BFB033B18E CRC64;
MHTPKHAIQR ISKEEMEFFE GRCERMGEAD ETMWGTKWCG SGNEATDISE LGYWSNLDSC
CRTHDHCDNI PSGQTKYGLT NEGKYTMMNC KCETAFEQCL RNVTGGMEGP AAGFVRKTYF
DLYGNGCYNV QCPSQRRLAR SEECPDGVAT YTGEAGYGAW AINKLNG
