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J. Biol. Chem., Vol. 276, Issue 42, 38690-38696, October 19, 2001
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From the Department of Biology, Georgia State University,
Atlanta, Georgia 30302-4010
The modulation of KATP channels
during acidosis has an impact on vascular tone, myocardial rhythmicity,
insulin secretion, and neuronal excitability. Our previous studies have
shown that the cloned Kir6.2 is activated with mild acidification but
inhibited with high acidity. The activation relies on His-175, whereas
the molecular basis for the inhibition remains unclear. To elucidate whether the His-175 is indeed the protonation site and what other structures are responsible for the pH-induced inhibition, we performed these studies. Our data showed that the His-175 is the only proton sensor whose protonation is required for the channel activation by
acidic pH. In contrast, the channel inhibition at extremely low pH
depended on several other histidine residues including His-186,
His-193, and His-216. Thus, proton has both stimulatory and inhibitory
effects on the Kir6.2 channels, which attribute to two sets of
histidine residues in the C terminus.
Distinct Histidine Residues Control the Acid-induced Activation
and Inhibition of the Cloned KATP Channel*
*
This work was supported by National Institutes of Health
Grant HL58410, American Diabetes Association Grant 1-01-RA-12, and American Heart Association Grant 9950528N.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
To whom correspondence should be addressed: Dept. of Biology,
Georgia State University, 24 Peachtree Center Ave., Atlanta, GA
30302-4010. Tel.: 404-651-0913; Fax: 404-651-2509; E-mail: cjiang@gsu.edu.
Copyright © 2001 by The American Society for Biochemistry and Molecular Biology, Inc.
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