Reviewed, UniProtKB/Swiss-Prot Q9TVX3 (KAX53_MESMA)

Names and origin

Protein names	Recommended name:     Potassium channel toxin alpha-KTx 5.3 Alternative name(s):     Neurotoxin BmP05     Potassium ion channel blocker P05
Organism	Mesobuthus martensii (Manchurian scorpion) (Buthus martensii)
Taxonomic identifier	34649 [NCBI]
Taxonomic lineage	Eukaryota › Metazoa › Arthropoda › Chelicerata › Arachnida › Scorpiones › Buthida › Buthoidea › Buthidae › Mesobuthus

Protein attributes

Sequence length	61 AA.
Sequence status	Complete.
Sequence processing	The displayed sequence is further processed into a mature form.
Protein existence	Evidence at protein level.

General annotation (Comments)

Function	Blocks small conductance calcium-activated potassium channels (KCNN, SK).
Subcellular location	Secreted.
Tissue specificity	Expressed by the venom gland.
Toxic dose	LD50 is 1.85 µg/kg by intracerebroventricular injection into mice. Ref.2 Ref.3
Miscellaneous	Toxicity experiments on mutants of Ref.3 are done without C-terminal amidation.
Sequence similarities	Belongs to the short scorpion toxin superfamily. Potassium channel inhibitor family. Alpha-KTx 5 subfamily.
Mass spectrometry	Molecular mass is 3371.39 Da from positions 29 - 59. Determined by MALDI. Ref.2

Ontologies

Keywords
Cellular component	Secreted
Domain	Signal
Molecular function	Ionic channel inhibitor Neurotoxin Potassium channel inhibitor Toxin
PTM	Amidation Disulfide bond
Technical term	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
	Signal peptide	1 – 28	28	Ref.2
	Chain	29 – 59	31	Potassium channel toxin alpha-KTx 5.3		PRO_0000035324
Amino acid modifications
	Modified residue	59	1	Histidine amide
	Disulfide bond	31 ↔ 49		By similarity
	Disulfide bond	36 ↔ 54		By similarity
	Disulfide bond	40 ↔ 56		By similarity
Experimental info
	Mutagenesis	34	1	K → A: 86.4% loss of toxicity. 100% loss of toxicity; when associated with A-41. Ref.3
	Mutagenesis	37	1	Q → P: 97.5% loss of toxicity. Ref.3
	Mutagenesis	41	1	R → A: 83.0% loss of toxicity. 100% loss of toxicity; when associated with A-34. Ref.3
	Mutagenesis	50 – 52	3	IGD → MNG: 68.4% loss of toxicity. Ref.3
	Mutagenesis	59	1	H → A: 55.4% loss of toxicity. Ref.3

Sequences

	Sequence		Length	Mass (Da)
	Q9TVX3-1 [UniParc]. Last modified May 1, 2000. Version 1. Checksum: 628B80BF2214E903	FASTA	61	6,808
	10 20 30 40 50 60 MHNYYKIVLI MVAFFAVIIT FSNIQVEGAV CNLKRCQLSC RSLGLLGKCI GDKCECVKHG K

References

[1]	"Genomic organization of three neurotoxins active on small conductance Ca2+-activated potassium channels from the scorpion Buthus martensi Karsch." Wu J.-J., Dai L., Lan Z.-D., Chi C.-W. FEBS Lett. 452:360-364(1999) [PubMed: 10386622] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA / MRNA].
[2]	"Characterization of four toxins from Buthus martensi scorpion venom, which act on apamin-sensitive Ca2+-activated K+ channels." Romi-Lebrun R., Martin-Eauclaire M.-F., Escoubas P., Wu F.Q., Lebrun B., Hisada M., Nakajima T. Eur. J. Biochem. 245:457-464(1997) [PubMed: 9151979] [Abstract] Cited for: PROTEIN SEQUENCE OF 29-59, SYNTHESIS, MASS SPECTROMETRY, LETHAL DOSE.
[3]	"Gene expression, mutation, and structure-function relationship of scorpion toxin BmP05 active on SK(Ca) channels." Wu J.-J., He L.-L., Zhou Z., Chi C.-W. Biochemistry 41:2844-2849(2002) [PubMed: 11851432] [Abstract] Cited for: MUTAGENESIS OF LYS-34; GLN-37; ARG-41; 50-ILE--ASP-52 AND HIS-59, LETHAL DOSE.

Cross-references

Sequence databases
EMBLGenBankDDBJ	AF079064 mRNA. Translation: AAD47378.1. AF095780 Genomic DNA. Translation: AAF03044.1.
3D structure databases
ModBase	Search...
Family and domain databases
InterPro	IPR001947. Scorpion_toxinS. [Graphical view]
Pfam	PF00451. Toxin_2. 1 hit. [Graphical view]
PROSITE	PS01138. SCORP_SHORT_TOXIN. 1 hit. [Graphical view]
ProtoNet	Search...

Entry information

Entry name

KAX53_MESMA

Accession

Primary (citable) accession number: Q9TVX3

Entry history

Integrated into UniProtKB/Swiss-Prot:	December 19, 2001
Last sequence update:	May 1, 2000
Last modified:	November 24, 2009
This is version 45 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation project

Tox-Prot (Toxin Annotation Project)