A family of orthologous proteins from centipede venoms inhibit the hKir6.2 channel.

Yajamana Ramu, Zhe Lu

Scientific reports 2019 Oct 01

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Inhibitors targeting ion channels are useful tools for studying their functions. Given the selectivity of any inhibitor for a channel is relative, more than one inhibitor of different affinities may be used to help identify the channel in a biological preparation. Here, we describe a family of small proteins in centipede venoms that inhibit the pore (hKir6.2) of a human ATP-sensitive K+ channel (hKATP). While the traditional peptide-sequencing service gradually vanishes from academic institutions, we tried to identify the sequences of inhibitory proteins purified from venoms by searching the sequences of the corresponding transcriptomes, a search guided by the key features of a known hKir6.2 inhibitor (SpTx1). The candidate sequences were cross-checked against the masses of purified proteins, and validated by testing the activity of recombinant proteins against hKir6.2. The four identified proteins (SsdTx1-3 and SsTx) inhibit hKATP channels with a Kd of <300 nM, compared to 15 nM for SpTx1. SsTx has previously been discovered to block human voltage-gated KCNQ K+ channels with a 2.5 μM Kd. Given that SsTx inhibits hKir6.2 with >10-fold lower Kd than it inhibits hKCNQ, SsTx may not be suitable for probing KCNQ channels in a biological preparation that also contains more-SsTx-sensitive KATP channels.

Citation

Yajamana Ramu, Zhe Lu. A family of orthologous proteins from centipede venoms inhibit the hKir6.2 channel. Scientific reports. 2019 Oct 01;9(1):14088