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Potassium channel toxin gamma-KTx 1.1

Centruroides noxius (Mexican scorpion)
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli


Blocks human and rat Kv11.1/KCNH2/ERG1 and Kv11.3/KCNH7/ERG3, as well as rat (but not human) Kv11.2/KCNH6/ERG2 (PubMed:11755529, PubMed:11864985, PubMed:16497878, PubMed:17369411, PubMed:20600425) by binding to channel outer vestibule (S5P domain) with a 1:1 stoichiometry (PubMed:11755529, PubMed:11864985, PubMed:17369411, PubMed:20600425). Inhibition data are the following: hERG1 (reversible, IC50~7 nM) (PubMed:11755529, PubMed:11864985, PubMed:16497878, PubMed:17369411, PubMed:20600425), rERG1 (reversible, Kd=6.8 nM) (PubMed:16497878), rERG2 (irreversible, Kd=2.8 nM) (PubMed:16497878), hERG3 (irreversible, Kd=4.05 nM) (PubMed:16497878) and rERG3 (reversible, Kd=38.1 nM) (PubMed:16497878) potassium channels. The toxin potency is not affected by elevating potassium ion concentration from 2 to 98 mM (PubMed:11864985). This toxin only blocks channels in a closed state (PubMed:12860380). At high toxin concentrations, block of Kv11.1/KCNH2/ERG1 macroscopic current is incomplete (93.5%). This suggests a kinetic mechanism model with two different states of toxin-channel binding (T+C=TC*=TC; in the TC* state, the toxin binds the channel but does not occlude the pore, whereas in the TC state the toxin binds and occludes the pore). In this model, incomplete block is explained by the relatively fast dissociation rate from the blocked channel conformation (TC) relative to the rate of conversion of the toxin-channel encounter complex (TC*) to the blocked channel conformation (TC) (PubMed:17369411).7 Publications


The affinity of the toxin for the channel decreases as temperature increases (Kd=7.3 nM and Kd=64 nM at 22 and 37 degrees Celsius, respectively), likely due to changes in the structure of the channel binding site.1 Publication
Does not affect the function of either mouse EAG/KCNH1 or ELK1 channels at concentration of 200 nM (PubMed:11755529). Does not inhibit hKv1.4/KCNA4, hKv4.3/KCND3, hKv2.1/KCNB1 and rKv7.1/KCNQ1 potassium channels at concentration of 50 nM (PubMed:11864985). Does not inhibit human Kv11.2/KCNH6/ERG2 (PubMed:16497878).3 Publications


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sitei33May represent the binding site1 Publication1
Sitei55Key residue on the interacting surface with the channel1 Publication1

GO - Molecular functioni


Molecular functionIon channel impairing toxin, Neurotoxin, Potassium channel impairing toxin, Toxin, Voltage-gated potassium channel impairing toxin

Names & Taxonomyi

Protein namesi
Recommended name:
Potassium channel toxin gamma-KTx 1.11 Publication
Alternative name(s):
Ergtoxin1 Publication
Short name:
CnErg11 Publication
Short name:
CnErgTx11 Publication
Short name:
ErgTx1 Publication
Short name:
ErgTx11 Publication
OrganismiCentruroides noxius (Mexican scorpion)
Taxonomic identifieri6878 [NCBI]
Taxonomic lineageiEukaryotaMetazoaEcdysozoaArthropodaChelicerataArachnidaScorpionesButhidaButhoideaButhidaeCentruroides

Subcellular locationi

Extracellular region or secreted Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi apparatus Nucleus Mitochondrion Manual annotation Automatic computational assertionGraphics by Christian Stolte; Source: COMPARTMENTS

Keywords - Cellular componenti


Pathology & Biotechi


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Mutagenesisi38Q → A: 6-fold reduction in affinity for Kv11.1/KCNH2/ERG1 potassium channel (Kd=72.9 nM). 1 Publication1
Mutagenesisi55M → A: 30-fold reduction in affinity for Kv11.1/KCNH2/ERG1 potassium channel (Kd=303.4 nM). 1 Publication1
Mutagenesisi62A → T: No change in affinity for Kv11.1/KCNH2/ERG1 potassium channel (Kd=14.2 nM). 1 Publication1

PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Signal peptidei1 – 201 PublicationAdd BLAST20
ChainiPRO_000003536221 – 62Potassium channel toxin gamma-KTx 1.1Add BLAST42

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Disulfide bondi25 ↔ 432 Publications
Disulfide bondi31 ↔ 542 Publications
Disulfide bondi40 ↔ 592 Publications
Disulfide bondi44 ↔ 612 Publications

Post-translational modificationi

After protein storage at -20 Celsius degrees during a couple of months, the Met-55 of a small number of toxins is naturally oxidized. This oxidized form is about three orders of magnitude less efficient (IC50=15 µM) than non-oxidized form.1 Publication

Keywords - PTMi

Disulfide bond


Tissue specificityi

Expressed by the venom gland.Curated


Secondary structure

Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Helixi25 – 27Combined sources3
Beta strandi33 – 35Combined sources3
Helixi38 – 47Combined sources10
Beta strandi48 – 50Combined sources3
Beta strandi52 – 57Combined sources6
Beta strandi59 – 61Combined sources3

3D structure databases

Select the link destinations:
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum

Miscellaneous databases


Family & Domainsi


The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin.
Has the CSalpha/beta fold, which comprises one or two short alpha helices connected to anti-parallel beta-sheets stabilized by three or four disulfide bonds.2 Publications

Sequence similaritiesi

Belongs to the ergtoxin family. Gamma-KTx 1 subfamily.Curated

Keywords - Domaini

Knottin, Signal

Family and domain databases

Gene3Di3.30.30.10. 1 hit.
InterProiView protein in InterPro
IPR012622. Ergtoxin.
IPR036574. Scorpion_toxin-like_sf.
PfamiView protein in Pfam
PF08086. Toxin_17. 1 hit.
ProDomiView protein in ProDom or Entries sharing at least one domain
PD736966. Ergtoxin. 1 hit.
SUPFAMiSSF57095. SSF57095. 1 hit.
PROSITEiView protein in PROSITE
PS60026. ERGTX. 1 hit.


Sequence statusi: Complete.

Sequence processingi: The displayed sequence is further processed into a mature form.

Q86QT3-1 [UniParc]FASTAAdd to basket

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Mass (Da):6,970
Last modified:June 1, 2003 - v1

Mass spectrometryi

Molecular mass is 4730.8±0.4 Da from positions 21 - 62. Determined by MALDI. 1 Publication

Sequence databases

Select the link destinations:
Links Updated
AY164271 mRNA. Translation: AAO22234.1.
AF288205 mRNA. Translation: AAG38523.1.

Entry informationi

Entry nameiKGX11_CENNO
AccessioniPrimary (citable) accession number: Q86QT3
Secondary accession number(s): Q9GQ92
Entry historyiIntegrated into UniProtKB/Swiss-Prot: October 31, 2003
Last sequence update: June 1, 2003
Last modified: November 22, 2017
This is version 72 of the entry and version 1 of the sequence. See complete history.
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programAnimal Toxin Annotation Program


Keywords - Technical termi

3D-structure, Direct protein sequencing