Assignment of voltage-gated potassium channel blocking activity to κ-KTx1.3, a non-toxic homologue of κ-hefutoxin-1, from Heterometrus spinifer venom
Assignment of voltage-gated potassium channel blocking activity to κ-KTx1.3, a non-toxic homologue of κ-hefutoxin-1, from Heterometrus spinifer venom
复制标题
DOI：
10.1016/j.bcp.2004.10.018
复制
发表时间：
2005-02-15
影响因子：
5.8
通讯作者：
Tytgat, J
中科院分区：
文献类型：
--
作者：
Nirthanan, S;Pil, J;Tytgat, J
一个新的家族的弱K+通道毒素（指定kappa-KTx）与一种新的“双螺旋”支架最近已被确定为来自异蝎（蝎科）毒液。基于最小功能二联体（Y 5和K19）的存在，研究了κ-肝毒素-1（kappa-KTx 1.1），发现其阻断Kv1.2（IC 50类似于40 μ M）和Kv1.3（IC 50类似于150 μ M）通道。本研究从刺异节蜱毒液中分离到一个与kappa-hefutoxin 1同源性约60%的kappa-KTx 1.3。有趣的是，尽管存在功能性二联体（Y 5和K19），kappa-KTx 1.3不能再现kappa-hefutoxin-1的K+通道阻断活性。由于kappa-KTx 1.3中的二联体赖氨酸侧接另一个赖氨酸（K20），因此假设该额外的正电荷可阻碍已知在二联体赖氨酸和Kv I通道选择性过滤器之间发生的关键静电相互作用。因此，合成了用中性（K20 A）或带负电荷（K20 E）或另一种带正电荷（K20 R）的氨基酸取代K20的κ-KTx 1.3突变体。kappa-KTx 1.3 K20 E，在亚型选择性和亲和力方面与kappa-hefutoxin I一致，产生Kv 1.2（IC 50 = 36.8 +/- 4.9 μ M）和Kv 1.3（IC 50 = 53.7 +/- 6.7 μ M）的阻断，但不产生Kv 1.1通道。k-KTx 1.3 K20 A产生Kv 1.2（IC 50 = 36.9 +/- 14.9 μ M）和Kv 1.3（IC 50 = 115.7 +/- 73 μ M）的阻断，此外，获得对Kv 1.1通道的亲和力（IC 50 = 110.7 +/- 7.7 μ M）。K20 R不能对所测试的通道亚型产生任何阻断。这些数据表明，在邻近二联体赖氨酸的位置中存在额外的带电残基阻碍了由kappa-KTx 1.3产生的Kv 1通道的功能性阻断。(C)2004年爱思唯尔公司All rights reserved.
A new family of weak K+ channel toxins (designated kappa-KTx) with a novel "bi-helical" scaffold has recently been characterized from Heterometrus fulvipes (Scorpionidae) venom. Based on the presence of the minimum functional dyad (Y5 and K19), kappa-hefutoxin-1 (kappa-KTx1.1) was investigated and found to block Kv 1.2 (IC50 similar to40 muM) and Kv 1.3 (IC50 similar to150 muM) channels. In the present study, kappa-KTx1.3, that shares similar to60% identity with kappa-hefutoxin 1, has been isolated from Heterometrus spinifer venom. Interestingly, despite the presence of the functional dyad (Y5 and K19), kappa-KTx1.3 failed to reproduce the K+ channel blocking activity Of kappa-hefutoxin-1. Since the dyad lysine in kappa-KTx1.3 was flanked by another lysine (K20), it was hypothesized that this additional positive charge could hinder the critical electrostatic interactions known to occur between the dyad lysine and the Kv I channel selectivity filter. Hence, mutants of kappa-KTx1.3, substituting K20 with a neutral (K20A) or a negatively (K20E) or another positively (K20R) charged amino acid were synthesized. kappa-KTx1.3 K20E, in congruence with kappa-hefutoxin I with respect to subtype selectivity and affinity, produced blockade of Kv 1.2 (IC50 = 36.8 +/- 4.9 muM) and Kv 1.3 (IC50 = 53.7 +/- 6.7 muM) but not Kv 1.1 channels. kappa-KTx 1.3 K20A produced blockade of both Kv 1.2 (IC50 = 36.9 +/- 14.9 muM) and Kv 1.3 (IC50 = 115.7 +/- 73 muM) and in addition, acquired affinity for Kv 1.1 channels (IC50 = 110.7 +/- 7.7 muM). kappa-KTx1.3 K20R failed to produce any blockade on the channel subtypes tested. These data suggest that the presence of an additional charged residue in a position adjacent to the dyad lysine impedes the functional block of Kv 1 channels produced by kappa-KTx1.3. (C) 2004 Elsevier Inc. All rights reserved.