Reviewed, UniProtKB/Swiss-Prot P08815 (KAX21_CENNO)

Names and origin

Protein names	Recommended name:     Potassium channel toxin alpha-KTx 2.1 Alternative name(s):     Noxiustoxin       Short name=NTx     Toxin II.11
Organism	Centruroides noxius (Mexican scorpion)
Taxonomic identifier	6878 [NCBI]
Taxonomic lineage	Eukaryota › Metazoa › Arthropoda › Chelicerata › Arachnida › Scorpiones › Buthida › Buthoidea › Buthidae › Centruroides

Protein attributes

Sequence length	39 AA.
Sequence status	Complete.
Sequence processing	The displayed sequence is not processed.
Protein existence	Evidence at protein level.

General annotation (Comments)

Function	Blocks voltage-gated non-inactivating potassium channels and unblocks inactivating potassium channels blocked by alpha-dendrotoxin in synaptosomes. Also displaces the alpha-dendrotoxin homolog dendrotoxin I from its receptor on brain synaptic membranes.
Subcellular location	Secreted.
Tissue specificity	Expressed by the venom gland.
Domain	The N-terminus is probably essential for channel affinity.
Miscellaneous	Is more effective than NTX2.
Sequence similarities	Belongs to the short scorpion toxin superfamily. Potassium channel inhibitor family. Alpha-KTx 2 subfamily.

Ontologies

Keywords
Cellular component	Secreted
Molecular function	Ionic channel inhibitor Neurotoxin Potassium channel inhibitor Toxin
PTM	Amidation Disulfide bond
Technical term	3D-structure Direct protein sequencing
Gene Ontology (GO)
Biological process	pathogenesis Inferred from electronic annotation. Source: UniProtKB-KW
Cellular component	extracellular region Inferred from electronic annotation. Source: UniProtKB-SubCell
Molecular function	potassium channel inhibitor activity Inferred from electronic annotation. Source: UniProtKB-KW
Complete GO annotation...

Sequence annotation (Features)

Feature key

Position(s)

Length

Description

Graphical view

Feature identifier

Molecule processing

Peptide

1 – 39

39

Potassium channel toxin alpha-KTx 2.1

PRO_0000044905

Regions

Region

26 – 34

9

Interaction with Ca(2+)-activated K(+) channels Potential

Amino acid modifications

Modified residue

39

1

Asparagine amide

Disulfide bond

7 ↔ 29

Ref.4

Disulfide bond

13 ↔ 34

Ref.4

Disulfide bond

17 ↔ 36

Ref.4

Secondary structure

1

.

.

.

.

.

.

.

.

39

Helix Strand Turn

Details...

Turn

14 – 16

3

Helix

17 – 20

4

Beta strand

27 – 30

4

Beta strand

33 – 36

4

Sequences

	Sequence		Length	Mass (Da)
	P08815-1 [UniParc]. Last modified July 19, 2004. Version 3. Checksum: 131DC4A78D497E0D	FASTA	39	4,202
	10 20 30 TIINVKCTSP KQCSKPCKEL YGSSAGAKCM NGKCKCYNN

References

[1]	"The primary structure of noxiustoxin. A K channel blocking peptide, purified from the venom of the scorpion Centruroides noxius Hoffmann." Possani L.D., Martin B.M., Svendsen I. Carlsberg Res. Commun. 47:285-289(1982) Cited for: PROTEIN SEQUENCE. Tissue: Venom.
[2]	"Synthetic peptides corresponding to the sequence of noxiustoxin indicate that the active site of this K+ channel blocker is located on its amino-terminal portion." Gurrola G.B., Molinar-Rode R., Sitges M., Bayon A., Possani L.D. J. Neural Transm. 77:11-20(1989) [PubMed: 2746197] [Abstract] Cited for: SYNTHESIS OF 1-9 AND 30-39.
[3]	"Structure revision of the scorpion toxin noxiustoxin through total chemical synthesis." Nutt R.F., Arison B.H., Smith J.S. (In) Schneider C.H., Eberles A.N. (eds.); Peptides 1992, pp.101-102, Escom Science Publishers, Leiden (1993) Cited for: SYNTHESIS, AMIDATION.
[4]	"Determination of the three-dimensional solution structure of noxiustoxin: analysis of structural differences with related short-chain scorpion toxins." Dauplais M., Gilquin B., Possani L.D., Gurrola-Briones G., Roumestand C., Menez A. Biochemistry 34:16563-16573(1995) [PubMed: 8527429] [Abstract] Cited for: STRUCTURE BY NMR, DISULFIDE BONDS.

Cross-references

3D structure databases

PDBPDBe

Entry	Method	Resolution (Å)	Chain	Positions	PDBsum
1SXM	NMR	-	A	1-39	[»]

ModBase

Search...

Family and domain databases

InterPro

IPR001947. Scorpion_toxinS.
[Graphical view]

Pfam

PF00451. Toxin_2. 1 hit.
[Graphical view]

PRINTS

PR00286. CHARYBDTOXIN.

ProDom

PD003586. Scorpion_toxinS. 1 hit.
[Graphical view] [Entries sharing at least one domain]

PROSITE

PS01138. SCORP_SHORT_TOXIN. 1 hit.
[Graphical view]

ProtoNet

Search...

Entry information

Entry name

KAX21_CENNO

Accession

Primary (citable) accession number: P08815

Entry history

Integrated into UniProtKB/Swiss-Prot:	November 1, 1988
Last sequence update:	July 19, 2004
Last modified:	June 16, 2009
This is version 72 of the entry and version 3 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

Tox-Prot (Toxin Annotation Project)