An Amino Acid Triplet in the NH2 Terminus of Rat ROMK1 Determines Interaction with SUR2B

Ke Dong, Jason Xu, Carlos G. Vanoye, Richard Welch, Gordon G. MacGregor, Gerhard Giebisch, Steven C. Hebert*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


ATP-regulated (KATP) channels are formed by an inward rectifier pore-forming subunit (Kir) and a sulfonylurea (glibenclamide)-binding protein, a member of the ATP binding cassette family (sulfonylurea receptor (SUR) or cystic fibrosis transmembrane conductance regulator). The latter is required to confer glibenclamide sensitivity to KATP channels. In the mammalian kidney ROMK1-3 are components of KATP channels that mediate K + secretion into urine. ROMK1 and ROMK3 splice variants share the core polypeptide of ROMK2 but also have distinct NH2-terminal extensions of 19 and 26 amino acids, respectively. The SUR2B is also expressed in rat kidney tubules and may combine with Kir.1 to form renal KATP channels. Our previous studies showed that co-expression of ROMK2, but not ROMK1 or ROMK3, with rat SUR2B in oocytes generated glibenclamide-sensitive K+ currents. These data suggest that the NH2-terminal extensions in both ROMK1 and ROMK3 block ROMK-SUR2B interaction. Seven amino acids in the NH2-terminal extensions of ROMK1 and ROMK3 are identical (amino acids 13-19 in ROMK1 and 20-26 in ROMK3) and may determine ROMK-SUR2B interaction. We constructed a series of hemagglutinin-tagged ROMK1 NH2-terminal deletion and substitution mutants and examined glibenclamide-sensitive K+ currents in oocytes when co-expressed with SUR2B. These studies identified an amino acid triplet "IRA" within the conserved segment in the NH2 terminus of ROMK1 and ROMK3 that blocks the ability of SUR2B to confer glibenclamide sensitivity to the expressed K+ currents. The position of this triplet in the ROMK1 NH2-terminal extension is also important for the ROMK-SUR2B interactions. In vitro co-translation and immunoprecipitation studies with hemagglutinin-tagged ROMK mutants and SUR2B indicted that direct interaction between these two proteins is required for glibenclamide sensitivity of induced K+ currents in oocytes. These results suggest that the IRA triplet in the NH2-terminal extensions of both ROMK1 and ROMK3 plays a key role in subunit assembly of the renal secretary KATP channel.

Original languageEnglish (US)
Pages (from-to)44347-44353
Number of pages7
JournalJournal of Biological Chemistry
Issue number47
StatePublished - Nov 23 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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