Interactions between charged residues in the transmembrane segments of the voltage-sensing domain in the hERG channel.
Studies on voltage-gated K channels such as Shaker have shown that positive charges in the voltage-sensor (S4) can form salt bridges with negative charges in the surrounding transmembrane segments in a state-dependent manner, and different charge pairings can stabilize the channels in closed or open states. The goal of this study is to identify such charge interactions in the hERG channel. This knowledge can provide constraints on the spatial relationship among transmembrane segments in the channel's voltage-sensing domain, which are necessary for modeling its structure. We first study the effects of reversing S4's positive charges on channel activation. Reversing positive charges at the outer (K525D) and inner (K538D) ends of S4 markedly accelerates hERG activation, whereas reversing the 4 positive charges in between either has no effect or slows activation. We then use the 'mutant cycle analysis' to test whether D456 (outer end of S2) and D411 (inner end of S1) can pair with K525 and K538, respectively. Other positive charges predicted to be able, or unable, to interact with D456 or D411 are also included in the analysis. The results are consistent with predictions based on the distribution of these charged residues, and confirm that there is functional coupling between D456 and K525 and between D411 and K538.
Department of Physiology, Virginia Commonwealth University, Richmond, VA 23298, USA.
M
M
Zhang
J
J
Liu
M
M
Jiang
D-M
DM
Wu
K
K
Sonawane
H R
HR
Guy
G-N
GN
Tseng
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism*; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000737:chemistry / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D055672:Static Electricity; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
D000596:Amino Acids; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D008565:Membrane Proteins