Interaction site for the inhibition of tarantula Jingzhaotoxin-XI on voltage-gated potassium channel Kv2.1.
Jingzhaotoxin-XI (JZTX-XI) is a 34-residue peptide from the Chinese tarantula Chilobrachys jingzhao venom that potently inhibits both voltage-gated sodium channel Nav1.5 and voltage-gated potassium channel Kv2.1. In the present study, we further showed that JZTX-XI blocked Kv2.1 currents with the IC50value of 0.39 ± 0.06 μM. JZTX-XI significantly shifted the current-voltage (I-V) curves and normalized conductance-voltage (G-V) curves of Kv2.1 channel to more depolarized voltages. Ala-scanning mutagenesis analyses demonstrated that mutants I273A, F274A, and E277A reduced toxin binding affinity by 10-, 16-, and 18-fold, respectively, suggesting that three common residues (I273, F274, E277) in the Kv2.1 S3b segment contribute to the formation of JZTX-XI receptor site, and the acidic residue Glu at the position 277 in Kv2.1 is the most important residue for JZTX-XI sensitivity. A single replacement of E277 with Asp(D) increased toxin inhibitory activity. These results establish that JZTX-XI inhibits Kv2.1 activation by trapping the voltage sensor in the rested state through a similar mechanism to that of HaTx1, but these two toxins have small differences in the most crucial molecular determinant. Furthermore, the in-depth investigation of the subtle differences in molecular determinants may be useful for increasing our understanding of the molecular details regarding toxin-channel interactions.
Department of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China; Division of Stem Cell Regulation and Application, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China. Electronic address: taohuai123@126.com.
Huai
H
Tao
Department of Orthopedics, The Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, China.
Xia
X
Chen
State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, Hunan 410013, China.
Meichun
M
Deng
Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China.
Yucheng
Y
Xiao
Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China.
Yuanyuan
Y
Wu
Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China.
Zhonghua
Z
Liu
Department of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China.
Sainan
S
Zhou
Department of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China; Division of Stem Cell Regulation and Application, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China.
Yingchun
Y
He
Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China. Electronic address: liangsp@hunnu.edu.cn.
Songping
S
Liang
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000633:toxicity*; D017386:Sequence Homology, Amino Acid; D051669:Shab Potassium Channels / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics; D013111:Spider Venoms / Q000633:toxicity*
D010455:Peptides; D051669:Shab Potassium Channels; D013111:Spider Venoms; C525630:jingzhaotoxin XI, Chilobrachys jingzhao
Jingzhaotoxin-XI; Kv2.1; Molecular determinant; Mutation