NDLI: MinK-KvLQT1 Fusion Proteins, Evidence for Multiple Stoichiometries of the Assembled I sK Channel

Content Provider	Journal of Biological Chemistry (JBC)
Author	Wang, Wenyan Xia, Jing Kass, Robert S.
Abstract	I sK, a slowly activating delayed rectifier K+ current through channels formed by the assembly of two channel proteins KvLQT1 and MinK, modulates the repolarization of cardiac action potentials. Mutations that map to theKvLQT1 and minK genes account for more than 50% of an inherited cardiac disorder, the Long QT syndrome (Splawski, I., Tristani-Firouzi, M., Lehmann, M. H., Sanguinetti, M. C., and Keating, M. T. (1997) Nat. Genet. 17, 338–340). Despite the importance of these channels to human cardiac function, the molecular basis of their uniquely slow gating properties as well as the stoichiometry and interaction sites of these two subunits are still unclear. We have constructed several fusion channel proteins to begin investigating the stoichiometry of these two subunits and the role of voltage-dependent subunit assembly in channel gating. Functional properties of these constructs were measured using whole cell patch clamp recordings of transiently transfected Chinese hamster ovary cells. The constructs we tested are as follows: MK24 (C terminus of MinK linked to N terminus of KvLQT1); KK40 (a tandem homodimer of KvLQT1); and MKK44 (C terminus of MinK linked to N terminus of KK40). In control experiments (no DNA, control DNA, or only MinK), no time-dependent K+ current was observed. Expression of KvLQT1 or KK40 produced currents that activate and inactivate in a voltage-dependent manner as reported by others for KvLQT1. In contrast, expression of MK24 and MKK44 elicited current with activation kinetics and voltage dependence very similar to native I sK and identical to currents expressed by cells co-transfected with independent MinK and KvLQT1 cDNA. Expression of MK24 plus additional MinK significantly slows current kinetics. Our data raise the possibility 1) of multiple MinK/KvLQT1 stoichiometries and 2) indicate that uniquely slow kinetics ofI sK channels is due to voltage-dependent conformational changes of the channel protein and not to assembly of channel subunits.
Related Links	http://www.jbc.org/content/273/51/34069.abstract
Ending Page	34074
Starting Page	34069
Page Count	6
File Format	HTM / HTML PDF
ISSN	00219258
Journal	Journal of Biological Chemistry (JBC)
Issue Number	51
Volume Number	273
DOI	10.1074/jbc.273.51.34069
e-ISSN	1083351X
Language	English
Publisher	American Society for Biochemistry and Molecular Biology
Publisher Date	1998-12-18
Access Restriction	Open
Subject Keyword	Long QT (LQT) Chinese hamster ovary (CHO) Kilobase pair (kb) Polymerase chain reaction. (PCR) PROTEIN CHEMISTRY AND STRUCTURE
Content Type	Text
Resource Type	Article
Subject	Cell Biology Biochemistry Molecular Biology

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