Di-Substituted Cyclohexyl Derivatives Bind to Two Identical Sites with Positive Cooperativity on the Voltage-Gated Potassium Channel, Kv1.3

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• 作者：William A. Schmalhofer ; Robert S. Slaughter ; Mary Matyskiela ; John P. Felix ; Yui S. Tang ; Kathleen Rupprecht ; Gregory J. Kaczorowski ; and Maria L. Garcia
• 刊名：Biochemistry
• 出版年：2003
• 出版时间：April 29, 2003
• 年：2003
• 卷：42
• 期：16
• 页码：4733 - 4743
• 全文大小：275K
• 年卷期：v.42,no.16(April 29, 2003)
• ISSN：1520-4995

文摘

Di-substituted cyclohexyl (DSC) derivatives inhibit the voltage-gated potassium channel, K_v1.3,and have immunosuppressant activity (Schmalhofer et al. (2002) Biochemistry 41, 7781-7794). Thisclass of inhibitors displays Hill coefficients of near 2 in functional assays, and trans DSC analoguesappear to selectively interact with K_v1.3 channel conformations related to C-type inactivation. To furtherunderstand the details of the DSC inhibitor interaction with potassium channels, trans-1-(N-n-propylcarbamoyloxy)-4-phenyl-4-(3-(2-methoxyphenyl)-3-oxo-2-azaprop-1-yl)cyclo-hexane (trans-NPCO-DSC) was radiolabeled with tritium, and its binding characteristics to K_v1.3 channels were determined.Specific binding of [³H]-trans-NPCO-DSC to K_v1.3 channels is a saturable, time-dependent, and fullyreversible process. Saturation binding isotherms and competition binding experiments are consistent withthe presence of two receptor sites for DSC derivatives on the K_v1.3 channel that display positive allostericcooperativity. The high affinity interaction of [³H]-trans-NPCO-DSC with K_v1.3 channels appears tocorrelate with the rates of C-type inactivation of the channel. These data, taken together, mark the firstdemonstration of the existence of multiple binding sites for an inhibitor of an ion channel and suggestthat the high affinity interaction of trans-NPCO-DSC and similar inhibitors with K_v1.3 channels could beexploited for the development of selective molecules that target this protein.