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Mutations in the linker domain of NBD2 of SUR inhibit transduction but not nucleotide binding
Author(s) -
Matsuo Michinori,
Dabrowski Michael,
Ueda Kazumitsu,
Ashcroft Frances M.
Publication year - 2002
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdf419
Subject(s) - biology , nucleotide , linker , transduction (biophysics) , genetics , binding site , mutation , cyclic nucleotide binding domain , microbiology and biotechnology , biochemistry , gene , computer science , operating system
ATP‐sensitive potassium (K ATP ) channels are composed of an ATP‐binding cassette (ABC) protein (SUR1, SUR2A or SUR2B) and an inwardly rectifying K + channel (Kir6.1 or Kir6.2). Like other ABC proteins, the nucleotide binding domains (NBDs) of SUR contain a highly conserved 'signature sequence’ (the linker, LSGGQ) whose function is unclear. Mutation of the conserved serine to arginine in the linker of NBD1 (S1R) or NBD2 (S2R) did not alter the ability of ATP or ADP (100 μM) to displace 8‐azido‐[ 32 P]ATP binding to SUR1, or abolish ATP hydrolysis at NBD2. We co‐expressed Kir6.2 with wild‐type or mutant SUR in Xenopus oocytes and recorded the resulting currents in inside‐out macropatches. The S1R mutation in SUR1, SUR2A or SUR2B reduced K ATP current activation by 100 μM MgADP, whereas the S2R mutation in SUR1 or SUR2B (but not SUR2A) abolished MgADP activation completely. The linker mutations also reduced (S1R) or abolished (S2R) MgATP‐dependent activation of Kir6.2‐R50G co‐expressed with SUR1 or SUR2B. These results suggest that the linker serines are not required for nucleotide binding but may be involved in transducing nucleotide binding into channel activation.