NEM modification prevents high-affinity ATP binding to the first nucleotide binding fold of the sulphonylurea receptor, SUR1.
Pancreatic beta-cell ATP-sensitive potassium channels, composed of SUR1 and Kir6.2 subunits, serve as a sensor for intracellular nucleotides and regulate glucose-induced insulin secretion. To learn more about the interaction of SUR1 with nucleotides, we examined the effect of N-ethylmaleimide (NEM) modification. Photoaffinity labeling of SUR1 with 5 microM 8-azido-[alpha-32P]ATP or 8-azido-[gamma-32P]ATP was inhibited by NEM with Ki of 1.8 microM and 2.4 microM, and Hill coefficients of 0.94 and 1.1, respectively. However, when the cysteine residue in the Walker A motif of the first nucleotide binding fold (NBF1) of SUR1 was replaced with serine (C717S), photoaffinity labeling was not inhibited by 100 microM NEM. These results suggest that NBF1 of SUR1 has a NEM-sensitive structure similar to that of NBF1 of MDR1, a multidrug transporter, and confirm NBF1 as the high-affinity ATP binding site on SUR1.
Matsuo
M
M
Division of Applied Life Sciences, Kyoto University Graduate School of Agriculture, Kyoto, Japan.
Tucker
S J
SJ
Ashcroft
F M
FM
Amachi
T
T
Ueda
K
K
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry; D018528:ATP-Binding Cassette Transporters; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000737:chemistry; D000818:Animals; D001386:Azides / Q000737:chemistry; D001665:Binding Sites / Q000187:drug effects; D019556:COS Cells; D006224:Cricetinae; D005033:Ethylmaleimide / Q000494:pharmacology; D009154:Mutation; D019920:Photoaffinity Labels; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D011955:Receptors, Drug / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D064233:Sulfonylurea Receptors; D014466:Ultraviolet Rays
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; C577509:Abcc8 protein, rat; D001386:Azides; D019920:Photoaffinity Labels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; C017040:8-azidoadenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D005033:Ethylmaleimide