The Study Of The Structure And Functions Of Peptides Activating KCNQ1/KCNE1 Potassium Channel

The typical delayed rectifier potassium channel is formed by KCNQ1 subunit and KCNE1 subunit, that can be expressed on HEK293T cell membrane and generates the delayed rectifier potassium current (DCs). KCNQ1 is the alpha subunit of the delayed rectifier potassium channel, mainly expressed in heart and closely related to regulation of rhythm. Mutations of KCNQ1 may directly or indirectly cause a series of heart diseases. The KCNE1 is the β subunit of delayed rectifier potassium channel, which can express with KCNQ1 and interact with each other, and the current of KCNQ1 expressed on the cell membrane increases about four times. In this study, I screened and purified the activator of KCNQ1/KCNE1 delayed rectifier potassium channel from Chinese tarantula (Chilobrachys jingzhao),and carried out the research of its structure and functions.By using reversed-phase high performance liquid chromatography, mass spectrometry and patch clamp electrophysiology experimental techniques, a peptide toxin purified from the venom of Chinese tarantula can induce the currents of the KCNQ1/KCNE1 delayed rectifier potassium channel. The relative molecular weight of the toxin is 3704.1. And through the Edman degradation sequencing,the sequence of the toxin is SCIERMQTCEVEAGLPCCSGAPCICPYIGDCICIQ,the amino acid sequence of the toxin is named chilobrachys toxin (JZTX-54). Patch-clamp electrophysio logical experiments indicate:1μmol/L JZTX-54 can significantly activate the KCNQ1/KCNE1 delayed rectifier potassium channel, making the current of KCNQ1/KCNE1 delayed rectifier potassium significantly increased. Meanwhile, JZTX-54 can activate the the KCNQ1/KCNE1 delayed rectifier potassium channel in a concentration-dependent manners, with EC50 value of 235nmol/L. Furthermore, according to the steady-state activation curve, JZTX-54 can alter the gating properties of the KCNQ1/KCNE1 delayed rectifier potassium by shifting the voltage dependence of channel activation to more positive voltages about 12mV from 36.90 ± 1.07mV to 24.53 ± 0.42mV. In order to prove the specificity of JZTX-54 to the KCNQ1/KCNE1 delayed rectifier potassium channel, I used the whole-cell patch-clamp technique to detect whether JZTX-54 effects voltage-gated sodium, potassium, calcium channel expressed on the rat dorsal root ganglion (DRG) cells.The experimental results show that JZTX-54 has no or weak inhibition on the sodium, potassium, calcium channel distributed on rat dorsal root ganglion (DRG) cells. This means that JZTX-54 has a good selectivity on the KCNQ1/KCNE1 delayed rectifier K+ channel, which can specific activation of KCNQ1/KCNE1 delayed rectifier potassium channels, has little effect on other ion channels, and has the potential to be developed into tools reagent for studying the KCNQ1/KCNEl delayed rectifier K+ channels or a new drug to treat heart disease.