P56637 (SIXE_BUTJU) Reviewed, UniProtKB/Swiss-Prot

Names and origin

Protein names

Recommended name:
Beta-insect excitatory toxin Bj-xtrIT
Short name=Bjxtr-IT
Short name=BjxtrIT

Gene names

Name:

XTRIT

Organism

Buthotus judaicus (Scorpion) (Hottentotta judaica)

Taxonomic identifier

6863 [NCBI]

Taxonomic lineage

cellular organisms › Eukaryota › Opisthokonta › Metazoa › Eumetazoa › Bilateria › Protostomia › Ecdysozoa › Panarthropoda › Arthropoda › Chelicerata › Arachnida › Scorpiones › Buthida › Buthoidea › Buthidae › Hottentotta

Protein attributes

Sequence length	94 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	Excitatory insect toxins induce a spastic paralysis. They bind voltage-independently at site-4 of sodium channels (Nav) and shift the voltage of activation toward more negative potentials thereby affecting sodium channel activation and promoting spontaneous and repetitive firing. This toxin is active only on insects.
Subcellular location	Secreted.
Tissue specificity	Expressed by the venom gland.
Toxic dose	Both variants Bjxtr-IT.56E and Bjxtr-IT.56K have an PD50 of 9.6 ng/100 mg of body weight of blowfly larvae. Ref.2
Sequence similarities	Belongs to the long (4 C-C) scorpion toxin superfamily. Sodium channel inhibitor family. Beta subfamily.
Mass spectrometry	Molecular mass is 8455 Da from positions 19 - 94. Ref.2

Ontologies

Keywords
Cellular component	Secreted
Domain	Signal
Molecular function	Ion channel impairing toxin Neurotoxin Sodium channel inhibitor Toxin
PTM	Disulfide bond
Technical term	3D-structure Direct protein sequencing
Gene Ontology (GO)
Biological_process	defense response Inferred from electronic annotation. Source: InterPro
Cellular_component	extracellular region Inferred from electronic annotation. Source: UniProtKB-SubCell
Molecular_function	sodium 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 – 18

18

Ref.2

Chain

19 – 94

76

Beta-insect excitatory toxin Bj-xtrIT

PRO_0000035199

Sites

Site

33

1

May be involved in voltage sensor trapping upon activation of sodium channel

Site

48

1

May interact with a positively charged residue of the receptor site

Amino acid modifications

Disulfide bond

34 ↔ 60

Disulfide bond

45 ↔ 65

Disulfide bond

49 ↔ 67

Disulfide bond

61 ↔ 87

Natural variations

Natural variant

56

1

E → K.

Experimental info

Mutagenesis

19

1

K → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

20

1

K → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

26

1

D → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

30

1

K → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

33

1

E → A: 47.5-fold decrease in toxicity and little effect on the binding affinity. Ref.4

Mutagenesis

33

1

E → F: 743-fold decrease in toxicity and little effect on the binding affinity. Ref.4

Mutagenesis

33

1

E → R: >10000-fold decrease in toxicity and little decrease in binding affinity. Ref.4

Mutagenesis

48

1

E → D: 8.3-fold decrease in toxicity and 43.6-fold decrease in binding affinity. Ref.4

Mutagenesis

48

1

E → L: 29-fold decrease in toxicity and 158-fold decrease in binding affinity. Ref.4

Mutagenesis

48

1

E → Q: 27.3-fold decrease in toxicity and 74.5-fold decrease in binding affinity. Ref.4

Mutagenesis

48

1

E → R: 608-fold decrease in toxicity and 11455-fold decrease in binding affinity. Ref.4

Mutagenesis

51

1

K → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

56

1

E → I: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

71 – 73

3

EDD → AAA: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

71 – 73

3

EDD → KRR: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

72

1

D → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

73

1

D → A: Little effect on toxicity and on the binding affinity.

Mutagenesis

74

1

K → T: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

81

1

D → N: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

84

1

K → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

85

1

K → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

88

1

D → A: Little effect on toxicity and on the binding affinity. Ref.4

Mutagenesis

93 – 94

2

Missing: 4.6-fold reduction of toxicity.

Mutagenesis

94

1

Missing: 5.7-fold reduction of toxicity.

Secondary structure

1

.

.

.

.

.

.

.

.

.

.

.

.

.

94

Helix Strand Turn

Details...

Beta strand

19 – 22

4

Helix

37 – 40

4

Helix

43 – 51

9

Beta strand

56 – 61

6

Beta strand

64 – 71

8

Helix

81 – 87

7

Sequences

	Sequence		Length	Mass (Da)
	P56637 [UniParc]. Last modified December 15, 1998. Version 1. Checksum: 40F6510F26E4BB90	FASTA	94	10,512
	10 20 30 40 50 60 MKFFLMCLII FPIMGVLGKK NGYPLDRNGK TTECSGVNAI APHYCNSECT KVYYAESGYC 70 80 90 CWGACYCFGL EDDKPIGPMK DITKKYCDVQ IIPS

References

[1]	"An excitatory scorpion toxin with a distinctive feature: an additional alpha helix at the C-terminus and its implications for interaction with insect sodium channels." Oren D.A., Froy O., Amit E., Kleinberger-Doron N., Gurevitz M., Shaanan B. Structure 6:1095-1103(1998) [PubMed] [Europe PMC] [Abstract] Cited for: NUCLEOTIDE SEQUENCE [MRNA], X-RAY CRYSTALLOGRAPHY (2.1 ANGSTROMS).
[2]	"The putative bioactive surface of insect-selective scorpion excitatory neurotoxins." Froy O., Zilberberg N., Gordon D., Turkov M., Gilles N., Stankiewicz M., Pelhate M., Loret E., Oren D.A., Shaanan B., Gurevitz M. J. Biol. Chem. 274:5769-5776(1999) [PubMed] [Europe PMC] [Abstract] Cited for: PROTEIN SEQUENCE OF 19-48, MASS SPECTROMETRY, PARALYTIC DOSE, MUTAGENESIS. Tissue: Venom.
[3]	"Dissection of the functional surface of an anti-insect excitatory toxin illuminates a putative 'hot spot' common to all scorpion beta-toxins affecting Na+ channels." Cohen L., Karbat I., Gilles N., Froy O., Corzo G., Angelovici R., Gordon D., Gurevitz M. J. Biol. Chem. 279:8206-8211(2004) [PubMed] [Europe PMC] [Abstract] Cited for: SYNTHESIS OF 19-94, MUTAGENESIS.
[4]	"Conversion of a scorpion toxin agonist into an antagonist highlights an acidic residue involved in voltage sensor trapping during activation of neuronal Na+ channels." Karbat I., Cohen L., Gilles N., Gordon D., Gurevitz M. FASEB J. 18:683-689(2004) [PubMed] [Europe PMC] [Abstract] Cited for: SYNTHESIS, MUTAGENESIS OF LYS-19; LYS-20; ASP-26; LYS-30; GLU-33; GLU-48; LYS-51; GLU-56; 71-GLU--ASP-73; ASP-72; LYS-74; ASP-81; LYS-84; LYS-85 AND ASP-88, SITE.
[5]	Erratum Karbat I., Cohen L., Gilles N., Gordon D., Gurevitz M. FASEB J. 18:947-947(2004)

Cross-references

Sequence databases

EMBL
GenBank
DDBJ

AJ012312 mRNA. Translation: CAA09987.1.
AJ012313 mRNA. Translation: CAA09988.1.

3D structure databases

PDBe
RCSB PDB
PDBj

Entry	Method	Resolution (Å)	Chain	Positions	PDBsum
1BCG	X-ray	2.10	A	19-94	[»]

ProteinModelPortal

P56637.

SMR

P56637. Positions 19-91.

ModBase

Search...

Protocols and materials databases

StructuralBiologyKnowledgebase

Search...

Family and domain databases

Gene3D

3.30.30.10. 1 hit.

InterPro

IPR003614. Scorpion_toxin-like.
[Graphical view]

SMART

SM00505. Knot1. 1 hit.
[Graphical view]

SUPFAM

SSF57095. SSF57095. 1 hit.

ProtoNet

Search...

Other

EvolutionaryTrace

P56637.

Entry information

Entry name

SIXE_BUTJU

Accession

Primary (citable) accession number: P56637

Entry history

Integrated into UniProtKB/Swiss-Prot:	December 15, 1998
Last sequence update:	December 15, 1998
Last modified:	May 1, 2013
This is version 78 of the entry and version 1 of the sequence. [Complete history]

Entry status

Reviewed (UniProtKB/Swiss-Prot)

Annotation program

Animal Toxin Annotation Program