title: Ginsenoside Rg3 inhibits human Kv1.4 channel currents by interacting with the Lys531 residue.
abstract: We have demonstrated previously that the 20(S) but not the 20(R) form of ginsenoside Rg(3) inhibited K(+) currents flowing through Kv1.4 (hKv1.4) channels expressed in Xenopus laevis oocytes, pointing to the presence of specific interaction site(s) for Rg(3) in the hKv1.4 channel. In the current study, we sought to identify this site(s). To this end, we first assessed how point mutations of various amino acid residues of the hKv1.4 channel affected inhibition by 20(S)-ginsenoside Rg(3) (Rg(3)). Lys531 residue is known to be a key site for K(+) activation and to be part of the extracellular tetraethylammonium (TEA) binding site; the mutation K531Y abolished the Rg(3) effect and made the Kv1.4 channel sensitive to TEA applied to the extracellular side of the membrane. Mutations of many other residues, including the pH sensitive-site (H507Q), were without any significant effect. We next examined whether K(+) and TEA could alter the effect of Rg(3) and vice versa. We found that 1) raising [K(+)](o) reduced the inhibitory effect of Rg(3) on hKv1.4 channel currents, whereas Rg(3) shifted the K(+) activation curve to the right, and 2) TEA caused a rightward shift of the Rg(3) concentration-response curve of wild-type hKv1.4 channel currents, whereas Rg(3) caused a rightward shift of the TEA concentration-response curve of K531Y mutant channel currents. The docked modeling revealed that Lys531 plays a key role in forming hydrogen bonds between Rg(3) and hKv1.4 channels. These results indicate that Rg(3) inhibits the hKv1.4 channel current by interacting with residue Lys531.
authors.affiliation: Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine, Konkuk University, Seoul 143-701 Korea.
authors.forename: Jun-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Byung-Hwan
authors.initials: BH
authors.lastname: Lee
authors.forename: Sun-Hye
authors.initials: SH
authors.lastname: Choi
authors.forename: In-Soo
authors.initials: IS
authors.lastname: Yoon
authors.forename: Mi Kyung
authors.initials: MK
authors.lastname: Pyo
authors.forename: Tae-Joon
authors.initials: TJ
authors.lastname: Shin
authors.forename: Woo-Sung
authors.initials: WS
authors.lastname: Choi
authors.forename: Yoongho
authors.initials: Y
authors.lastname: Lim
authors.forename: Hyewhon
authors.initials: H
authors.lastname: Rhim
authors.forename: Kwang Hee
authors.initials: KH
authors.lastname: Won
authors.forename: Yong Whan
authors.initials: YW
authors.lastname: Lim
authors.forename: Han
authors.initials: H
authors.lastname: Choe
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kim
authors.forename: Yang In
authors.initials: YI
authors.lastname: Kim
authors.forename: Seung-Yeol
authors.initials: SY
authors.lastname: Nah
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D004305:Dose-Response Relationship, Drug; D005260:Female; D036145:Ginsenosides / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D006860:Hydrogen Bonding; D020128:Inhibitory Concentration 50; D051665:Kv1.4 Potassium Channel / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D008239:Lysine / Q000378:metabolism*; D008958:Models, Molecular; D015394:Molecular Structure; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011485:Protein Binding; D019789:Tetraethylammonium / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D036145:Ginsenosides; D051665:Kv1.4 Potassium Channel; D026902:Potassium Channel Blockers; C097367:ginsenoside Rg3; D019789:Tetraethylammonium; D008239:Lysine