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Molecular structure of the glibenclamide binding site of the β‐cell K ATP channel
Author(s) -
Mikhailov Michael V,
Mikhailova Ellina A,
Ashcroft Stephen J.H
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02538-8
Subject(s) - glibenclamide , sulfonylurea receptor , binding site , biology , biochemistry , nucleotide , chemistry , biophysics , endocrinology , gene , diabetes mellitus
We have investigated the structure of the glibenclamide binding site of pancreatic β‐cell ATP‐sensitive potassium (K ATP ) channels. K ATP channels are a complex of four pore‐forming Kir6.2 subunits and four sulfonylurea receptor (SUR1) subunits. SUR1 (ABCC8) belongs to the ATP binding cassette family of proteins and has two nucleotide binding domains (NBD1 and NBD2) and 17 putative transmembrane (TM) sequences. Co‐expression in a baculovirus expression system of two parts of SUR1 between NBD1 and TM12 leads to restoration of glibenclamide binding activity, whereas expression of either individual N‐ or C‐terminal part alone gave no glibenclamide binding activity, confirming a bivalent structure of the glibenclamide binding site. By using N‐terminally truncated recombinant proteins we have shown that CL3 – the cytosolic loop between TM5 and TM6 – plays a key role in formation of the N‐terminal component of the glibenclamide binding site. Analysis of deletion variants of the C‐terminal part of SUR1 showed that CL8 – the cytosolic loop between TM15 and TM16 – is the only determinant for the C‐terminal component of the glibenclamide binding site. We suggest that in SUR1 in the native K ATP channel close proximity of CL3 and CL8 leads to formation of the glibenclamide binding site.