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Echinobase
ECB-ART-38147
Biochem J 2003 Nov 01;375Pt 3:805-12. doi: 10.1042/BJ20030672.
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Modulation of NAADP (nicotinic acid-adenine dinucleotide phosphate) receptors by K+ ions: evidence for multiple NAADP receptor conformations.

Dickinson GD , Patel S .


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NAADP (nicotinic acid-adenine dinucleotide phosphate) mediates Ca2+ release from intracellular Ca2+ stores in a wide variety of cell types. In sea urchin eggs, subthreshold concentrations of NAADP can cause full inactivation of NAADP-induced Ca2+ release, an effect that may be related to the ability of the target protein to bind its ligand in an essentially irreversible manner. In the present study, we found that K+ ions inhibit dissociation of NAADP from sea urchin egg homogenates. In low K+-containing media, an addition of excess unlabelled NAADP effectively displaced bound radioligand whereas dilution of radioligand initiated only partial dissociation. The inhibitory effects of K+ on dissociation of NAADP were concentration dependent, reversible and persisted after detergent solubilization. Lowering [K+] of the medium decreased the sensitivity of NAADP receptors for their ligand in stimulating Ca2+ release, but it did not affect inactivation of NAADP-induced Ca2+ release by subthreshold concentrations of NAADP. Our results are consistent with the observation of multiple conformations of the NAADP receptor that are readily revealed in low K+-containing media.

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Genes referenced: LOC100887844 LOC115919910 LOC576539

References [+] :
Aarhus, Activation and inactivation of Ca2+ release by NAADP+. 1996, Pubmed, Echinobase