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Photoaffinity labeling of high affinity nicotinic acid adenine dinucleotide phosphate (NAADP)-binding proteins in sea urchin egg. J Biol Chem 2012 Jan 20;287(4):2308-15



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2-s2.0-84856075676   75 Citations


Nicotinic acid adenine dinucleotide phosphate (NAADP) is a messenger that regulates calcium release from intracellular acidic stores. Recent studies have identified two-pore channels (TPCs) as endolysosomal channels that are regulated by NAADP; however, the nature of the NAADP receptor binding site is unknown. To further study NAADP binding sites, we have synthesized and characterized [(32)P-5-azido]nicotinic acid adenine dinucleotide phosphate ([(32)P-5N(3)]NAADP) as a photoaffinity probe. Photolysis of sea urchin egg homogenates preincubated with [(32)P-5N(3)]NAADP resulted in specific labeling of 45-, 40-, and 30-kDa proteins, which was prevented by inclusion of nanomolar concentrations of unlabeled NAADP or 5N(3)-NAADP, but not by micromolar concentrations of structurally related nucleotides such as NAD, nicotinic acid adenine dinucleotide, nicotinamide mononucleotide, nicotinic acid, or nicotinamide. [(32)P-5N(3)]NAADP binding was saturable and displayed high affinity (K(d) ∼10 nM) in both binding and photolabeling experiments. [(32)P-5N(3)]NAADP photolabeling was irreversible in a high K(+) buffer, a hallmark feature of NAADP binding in the egg system. The proteins photolabeled by [(32)P-5N(3)]NAADP have molecular masses smaller than the sea urchin TPCs, and antibodies to TPCs do not detect any immunoreactivity that comigrates with either the 45-kDa or the 40-kDa photolabeled proteins. Interestingly, antibodies to TPC1 and TPC3 were able to immunoprecipitate a small fraction of the 45- and 40-kDa photolabeled proteins, suggesting that these proteins associate with TPCs. These data suggest that high affinity NAADP binding sites are distinct from TPCs.

Author List

Walseth TF, Lin-Moshier Y, Jain P, Ruas M, Parrington J, Galione A, Marchant JS, Slama JT


Jonathan S. Marchant PhD Chair, Professor in the Cell Biology, Neurobiology and Anatomy department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Binding Sites
Calcium Channels
Photoaffinity Labels
Protein Binding
Strongylocentrotus purpuratus
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a