Activation of the archaeal ion channel MthK is exquisitely regulated by temperature

• Main Authors: Yihao Jiang, Vinay Idikuda, Sandipan Chowdhury, Baron Chanda
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2020-12-01
• Series: eLife
• Subjects: allosteric coupling; thermo-sensing; archaebacteria; ion channels; RCK domain; calcium activation
• Online Access: https://elifesciences.org/articles/59055

Physiological response to thermal stimuli in mammals is mediated by a structurally diverse class of ion channels, many of which exhibit polymodal behavior. To probe the diversity of biophysical mechanisms of temperature-sensitivity, we characterized the temperature-dependent activation of MthK, a two transmembrane calcium-activated potassium channel from thermophilic archaebacteria. Our functional complementation studies show that these channels are more efficient at rescuing K+ transport at 37°C than at 24°C. Electrophysiological activity of the purified MthK is extremely sensitive (Q10 >100) to heating particularly at low-calcium concentrations whereas channels lacking the calcium-sensing RCK domain are practically insensitive. By analyzing single-channel activities at limiting calcium concentrations, we find that temperature alters the coupling between the cytoplasmic RCK domains and the pore domain. These findings reveal a hitherto unexplored mechanism of temperature-dependent regulation of ion channel gating and shed light on ancient origins of temperature-sensitivity.