ISSN:
1432-2013
Keywords:
Key words Phosphorylation
;
Mg-ATP
;
AMP-PNP
;
AMP-PCP
;
ATP[γS]
;
Alkaline phosphatase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Ca2+-activated K+ channels in the basolateral plasma membrane of bullfrog oxynticopeptic cells are intimately involved in the regulation of acid secretion. Patch-clamp techniques were applied to study the regulating mechanism of these channels. In the excised inside-out configuration, intracellular Mg2+ decreased channel activity in a dose-dependent manner. In the absence of Mg2+, administration of adenosine 5′-triphosphate (ATP) to the cytoplasmic side also inhibited channel activity. On the other hand, in the presence of Mg2+, addition of ATP markedly increased channel activity. At a fixed concentration of free Mg2+, the Mg-ATP complex caused channel activation and shifted the dose response relationship between channel activity and the intracellular Ca2+ concentration to the left. A nonhydrolysable ATP analogue, adenosine 5′-[β,γ-imido]triphosphate (AMP-PNP) adenylyl [β,γ-methylene]diphosphate (AMP-PCP), could not substitute for ATP in channel activation, but a hydrolysable ATP analogue, adenosine 5′-O-(3-thiotriphosphate) (ATP[γS]) could do so. Furthermore, application of alkaline phosphatase to the cytoplasmic side inhibited channel activity. These results demonstrate that Ca2+-activated K+ channels are regulated by Mg2+ and ATP, and suggest that a phosphorylation reaction may be involved in the regulation mechanism of these channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050027
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