The kaliotoxin family enlarged. Purification, characterization, and precursor nucleotide sequence of KTX2 from Androctonus australis venom.
Kaliotoxin (KTX) has been originally described as an inhibitor of the intermediate conductance Ca(2+)-activated K+ channel (Crest, M., Jacquet, G., Gola, M., Zerrouk, H., Benslimane, A., Rochat, H., Mansuelle, P., and Martin-Eauclaire, M.-F. (1992) J. Biol. Chem. 267, 1640-1647). However, the radioiodinated 125I-KTX-(1-37) was also able to bind to the dendrotoxin sensitive voltage-dependent K+ channel (Romi, R., Crest, M., Gola, M., Sampieri, F., Jacquet, G., Zerrouk, H., Mansuelle, P., Sorokine, O., Van Dorsselaer, A., Rochat, H., Martin-Eauclaire, M.-F., and Van Rietschoten, J. (1993) J. Biol. Chem. 268, 26302-26309). By following the ability to compete with 125I-KTX-(1-37) for binding to its receptor on rat brain synaptosomes, a new kaliotoxin-like peptide, KTX2, was isolated from Androctonus australis scorpion venom. It is a 37-amino acid residue peptide, and its sequence shares 76% identity with KTX. The differences between the two peptides concern the NH2-terminal region and the residues 31 and 34 located in the region involved in the channel recognition. These differences may explain the 5-fold decrease of the molluscan Ca(2+)-activated K+ channel blockage by KTX2 (kd = 135 nM) as well as of its binding affinity to rat brain synaptosomes (IC50 = 50 pM), compared with KTX. Specific antibodies raised against KTX-(1-37) were not able to recognize KTX2. Using degenerate primers, a 370-base pair cDNA encoding the KTX2 precursor was amplified by polymerase chain reaction from a cDNA library of A. australis venom glands. It encoded a presumed signal peptide of 22 residues followed by the sequence of the mature peptide.
Laraba-Djebari
F
F
Laboratoire de Biochimie, Ingénierie des Protéines, URA 1455, Centre National de la Recherche Scientifique, Faculté de Médecine Nord, Marseille, France.
Legros
C
C
Crest
M
M
Céard
B
B
Romi
R
R
Mansuelle
P
P
Jacquet
G
G
van Rietschoten
J
J
Gola
M
M
Rochat
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001667:Binding, Competitive; D001921:Brain / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D018076:DNA, Complementary; D006372:Helix, Snails; D007700:Kinetics; D007928:Lethal Dose 50; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D012604:Scorpion Venoms / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism / Q000633:toxicity; D012605:Scorpions; D013574:Synaptosomes / Q000187:drug effects
D018076:DNA, Complementary; D015221:Potassium Channels; D012604:Scorpion Venoms; C072276:kaliotoxin; D002118:Calcium