Mutations in the S4 domain of a pacemaker channel alter its voltage dependence

FEBS Letters

Vaca, L.¹  Stieber, J.²  Ludwig, A.²  Biel, M.²  Zong, X.²  Hofmann, F.² 

[1] Departamento de Biologia Celular, Instituto de Fisiologia Celular, UNAM, Ciudad Universitaria, Mexico DF 04510, Mexico;Institut für Pharmakologie und Toxikologie der Technischen Universität München, Biedersteiner Straβe 29, 80802 Munich, Germany

关键词: HCN channel;    Voltage sensor;    Mutation;    Electrophysiology;   

DOI  :  10.1016/S0014-5793(00)01837-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

In an attempt to study the functional role of the positively charged amino acids present in the S4 segment of hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels, we have introduced single and sequential amino acid replacements throughout this domain in the mouse type 2 HCN channel (mHCN2). Sequential neutralization of the first three positively charged amino acids resulted in cumulative shifts of the midpoint voltage activation constant towards more hyperpolarizing potentials. The contribution of each amino acid substitution was approximately −20 mV. Amino acid replacements to neutralize either the first (K291Q) or fourth (R300Q) positively charged amino acid resulted in the same shift (about −20 mV) towards more hyperpolarized potentials. Replacing the first positively charged amino acid with the negatively charged glutamic acid (K291E) produced a shift of approximately −50 mV in the same direction. None of the above amino acid substitutions had any measurable effect on the time course of channel activation. This suggests that the S4 domain of HCN channels critically controls the voltage dependence of channel opening but is not involved in regulating activation kinetics. No channel activity was detected in mutants with neutralization of the last six positively charged amino acids from the S4 domain, suggesting that these amino acids cannot be altered without impairing channel function.

【 授权许可】

Unknown