Laraba-Djebari F, Legros C, Crest M, Céard B, Romi R, Mansuelle P, Jacquet G, van Rietschoten J, Gola M, Rochat H
Laboratoire de Biochimie, Ingénierie des Protéines, URA 1455, Centre National de la Recherche Scientifique, Faculté de Médecine Nord, Marseille, France.
J Biol Chem. 1994 Dec 30;269(52):32835-43.
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.
最初，卡利毒素（KTX）被描述为一种中间电导钙激活钾通道的抑制剂（克雷斯特，M.，雅凯，G.，戈拉，M.，泽鲁克，H.，本斯利马内，A.，罗沙特，H.，曼叙勒，P.，以及马丁 - 欧克莱尔，M.-F.（1992年）《生物化学杂志》267卷，第1640 - 1647页）。然而，放射性碘化的125I - KTX -（1 - 37）也能够与树眼镜蛇毒素敏感的电压依赖性钾通道结合（罗米，R.，克雷斯特，M.，戈拉，M.，桑皮耶里，F.，雅凯，G.，泽鲁克，H.，曼叙勒，P.，索罗金，O.，范多塞尔拉尔，A.，罗沙特，H.，马丁 - 欧克莱尔，M.-F.，以及范里特肖滕，J.（1993年）《生物化学杂志》268卷，第26302 - 26309页）。通过追踪与125I - KTX -（1 - 37）竞争结合大鼠脑突触体上其受体的能力，从澳大利亚杀人蝎毒液中分离出一种新的类卡利毒素肽，KTX2。它是一种由37个氨基酸残基组成的肽，其序列与KTX有76%的同源性。这两种肽之间的差异涉及氨基末端区域以及位于通道识别相关区域的第31和34位残基。与KTX相比，这些差异可能解释了KTX2对软体动物钙激活钾通道的阻断作用（kd = 135 nM）及其与大鼠脑突触体的结合亲和力（IC50 = 50 pM）下降了5倍的原因。针对KTX -（1 - 37）产生的特异性抗体无法识别KTX2。使用简并引物，通过聚合酶链反应从澳大利亚杀人蝎毒腺的cDNA文库中扩增出一个编码KTX2前体的370个碱基对的cDNA。它编码一个推测的由22个残基组成的信号肽，随后是成熟肽的序列。
