Ctri9577 (α-KTx15.10) is a neurotoxin present in the venom of the Chaerilus tricostatus scorpion, which is a potent blocker of the voltage-gated potassium channel Kv1.3, and a gating modifier of Kv4.3 channels.[1][2]
| Source | Chaerilus tricostatus (scorpion)[1] |
| Subfamily | α-KTx15[1] |
| Sequence (Signal sequence) (Mature protein) | MKLVMRILLTCFLLTTLVIKAEGQIHTNQPCTSNN
TRCRTYCIKVHKINSGKCMNSKCVCHP[1] |
| Molecular weight | 4439.7 Da[1] |
| Uniprot | P0DJO5 |
Etymology and Source
editThe Ctri9577 toxin is a component of the venom of the scorpion Chaerilus tricostatus.[1] The name of the toxin derives from the first letter of the genus of Chaerilus (C), species (tri), and the clone number in the cDNA library (9577).
Chemistry
editCtri9577 is a member of the α-KTx15 subfamily, which specifically target potassium channels. The mature peptide of Ctri9577, which is the peptide without the signal sequence, consists of 39 amino acids (4.44 kDa), including six cysteines which form three disulfide bridges (see table 1).[1] Other scorpion toxins specific for K+ channels (KTx) commonly form a CSα/β (cysteine-stabilized α-helix-β-sheet) fold.[1] [4] In this motif, an α-helix is connected to two or three antiparallel β-sheets and stabilized with disulfide bridges.
The predicted secondary structure of Ctri9577 is based on the typical fold of other scorpion KTxs; it consists of an α-helix connected to three antiparallel β-sheets, which is stabilized with three disulfide bridges (see figure 1).
Ctri9577 has low sequence similarity (<50%) with most other members of the α-KTx15 subfamily.,[1] placing it far away on the phylogenetic tree.[1] [5]
Target
editCtri9577 is a toxin specific for voltage-gated potassium channels, which functions both as a potent Kv1.3 channel-blocker[1] and a gating modifier of Kv4.3 channels.[2] The Kv1.3 channels are inhibited with an IC50 of 0.49 ± 0.45 nM.[1] Ctri9577 also modifies the gating of Kv4.3 channels through binding with the S3b-S4 linker within the voltage-sensing domain of the channel, in which four residues are of importance: L275, V276, N280, and V288.[2][6][7] Ctri9577’s inhibition of Kv4.3 channel currents is much less potent (IC50-value of 1.34 ± 0.03 μM) than the block of Kv1.3 channels.[2]
Mode of action
editThe inhibitory effect of Ctri9577 on Kv1.3 channels is voltage-independent.[1][2] The blocking of the delayed rectifier Kv1.3 is expected to slow down the repolarization phase of the action potential.
Ctri9577's effect on Kv4.3 gating occurs through:[2]
- shifting activation to more positive potentials
- shifting steady-state inactivation curves to more positive potentials, and
- slower recovery from open-state inactivation.
As a result, Kv4.3 channels will be inhibited.
References
edit- ^ a b c d e f g h i j k l m Xie, Shujun; Feng, Jing; Yu, Congya; Li, Zhi; Wu, Yingliang; Cao, Zhijian; Li, Wenxin; He, Xiaohua; Xiang, Ming; Han, Song (July 2012). "Identification of a new specific Kv1.3 channel blocker, Ctri9577, from the scorpion Chaerilus tricostatus". Peptides. 36 (1): 94–99. doi:10.1016/j.peptides.2012.04.023. PMID 22580271. S2CID 20286033.
- ^ a b c d e f Xie, Chang; Li, Tian; Xu, Lingna; Yu, Congya; Cao, Zhijian; Li, Wenxin; Wu, Yingliang (February 2014). "Kv1.3 potassium channel-blocking toxin Ctri9577, novel gating modifier of Kv4.3 potassium channel from the scorpion toxin family". Biochemical and Biophysical Research Communications. 444 (3): 406–410. doi:10.1016/j.bbrc.2014.01.094. PMID 24472546.
- ^ "AlphaFold Protein Structure Database". alphafold.ebi.ac.uk.
- ^ Mouhat, Stéphanie; Jouirou, Besma; Mosbah, Amor; De Waard, Michel; Sabatier, Jean-Marc (15 March 2004). "Diversity of folds in animal toxins acting on ion channels". Biochemical Journal. 378 (3): 717–726. doi:10.1042/BJ20031860. PMC 1224033. PMID 14674883.
- ^ Ding, Li; Chen, Jing; Hao, Jinbo; Zhang, Jiahui; Huang, Xuejun; Hu, Fangfang; Wu, Zheng; Liu, Yaru; Li, Wenxin; Cao, Zhijian; Wu, Yingliang; Li, Jian; Li, Shan; Liu, Hongyan; Wu, Wenlong; Chen, Zongyun (May 2017). "Discovery of three toxin peptides with Kv1.3 channel and IL-2 cytokine-inhibiting activities from Non-Buthidae scorpions, Chaerilus tricostatus and Chaerilus tryznai". Peptides. 91: 13–19. doi:10.1016/j.peptides.2017.03.005. PMID 28300672. S2CID 3475746.
- ^ Yarov-Yarovoy, Vladimir; Baker, David; Catterall, William A. (9 May 2006). "Voltage sensor conformations in the open and closed states in rosetta structural models of K + channels". Proceedings of the National Academy of Sciences. 103 (19): 7292–7297. Bibcode:2006PNAS..103.7292Y. doi:10.1073/pnas.0602350103. PMC 1464335. PMID 16648251.
- ^ Zhang, Yiya; Luo, Ji; He, Juan; Rong, Mingqiang; Zeng, Xiongzhi (16 April 2019). "JZTX-V Targets the Voltage Sensor in Kv4.2 to Inhibit Ito Potassium Channels in Cardiomyocytes". Frontiers in Pharmacology. 10: 357. doi:10.3389/fphar.2019.00357. PMC 6476928. PMID 31040778.