ECB-ART-37554
Biochem Biophys Res Commun
2000 Sep 16;2761:112-6. doi: 10.1006/bbrc.2000.3444.
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Characterization of NAADP(+) binding in sea urchin eggs.
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Nicotinic acid adenine dinucleotide phosphate (NAADP(+)) is a pyridine nucleotide which has been shown to release Ca(2+) from intracellular membranes in echinoderms, Ascidiae, mammals, and plants. NAADP releases Ca(2+) via a mechanism independent of ryanodine and inositol 1,4,5-trisphosphate (IP(3)) receptors and the NAADP(+) receptor is likely to be located on a separate organelle. We have investigated the binding characteristics of NAADP(+) to its receptor in sea urchin egg homogenates. NAADP(+) binds to a saturable membrane-bound site with high affinity (K(d) = 193 +/- 35. 7 pM). NAADP(+) associates to its receptor with a t(1/2) of approximately 7 min while dissociation does not occur during the time course of the experiment. Furthermore, NAD(+), NAAD(+), ADP, or ATP cannot displace NAADP(+) binding. The structurally related molecules NADP(+) and NADPH displayed a markedly lower affinity for the binding site with K(d)''s 500- and 25,000-fold higher than NAADP(+), respectively. This discrepancy between oxidized and reduced forms of NADP(+) might suggest that NAADP(+) signaling is itself regulated by the redox state of the cell.
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???displayArticle.link??? Biochem Biophys Res Commun
Genes referenced: LOC100887844 LOC115919080 LOC115919910 LOC576539