Cardiolipin binding enhances KcsA channel gating via both its specific and dianion-monoanion interchangeable sites

Masayuki Iwamoto; Masayuki Morito; Shigetoshi Oiki; Yudai Nishitani; Daisuke Yamamoto; Nobuaki Matsumori

doi:10.1016/j.isci.2023.108471

Cardiolipin binding enhances KcsA channel gating via both its specific and dianion-monoanion interchangeable sites

iScience. 2023 Nov 14;26(12):108471. doi: 10.1016/j.isci.2023.108471. eCollection 2023 Dec 15.

Authors

Masayuki Iwamoto¹, Masayuki Morito², Shigetoshi Oiki³, Yudai Nishitani⁴, Daisuke Yamamoto⁴, Nobuaki Matsumori²

Affiliations

¹ Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan.
² Department of Chemistry, Graduate School of Science, Kyushu University, Fukuoka 819-0395 Japan.
³ Biomedial Imaging Research Center, University of Fukui, Fukui 910-1193, Japan.
⁴ Department of Applied Physics, Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan.

Abstract

KcsA is a potassium channel with a plethora of structural and functional information, but its activity in the KcsA-producing actinomycete membranes remains elusive. To determine lipid species involved in channel-modulation, a surface plasmon resonance (SPR)-based methodology, characterized by immobilization of membrane proteins under a membrane environment, was applied. Dianionic cardiolipin (CL) showed extremely higher affinity for KcsA than monoanionic lipids. The SPR experiments further demonstrated that CL bound not only to the N-terminal M0 helix, a lipid-sensor domain, but to the M0 helix-deleted mutant. In contrast, monoanionic lipids interacted primarily with the M0 helix. This indicates the presence of an alternative CL-binding site, plausibly in the transmembrane domain. Single-channel recordings demonstrated that CL enhanced channel opening in an M0-independent manner. Taken together, the action of monoanionic lipids is exclusively mediated by the M0 helix, while CL binds both the M0 helix and its specific site, further enhancing the channel activity.

Keywords: Biochemistry; Biological sciences; Membrane architecture.