Molecular site for nucleotide binding on an ATP-sensitive renal K+ channel (ROMK2).

Academic Article

Abstract

  • ATP-sensitive, inwardly rectifying K+ channels are present in apical membranes of the distal nephron and play a major role in K+ recycling and secretion. The cloned renal K+ channel, ROMK1, is a candidate for the renal epithelial K+ channel, since it shares many functional characteristics with the native channel. Additionally, ROMK1 contains a putative carboxy-terminal ATP-binding site. Although ROMK1 channel activity could be reactivated by cytosolic Mg-ATP after rundown, the role of nucleotides in channel gating was less certain. We now show that an alternatively spliced transcript of the ROMK channel gene, ROMK2, which encodes a K+ channel with a truncated amino terminus, expresses an ATP-regulated and ATP-sensitive K+ channel (IKATP). Differences in the amino terminus of ROMK isoforms alters the sensitivity of the channel-gating mechanism to ATP. To test whether ATP sensitivity of renal IKATP is mediated by direct interaction of nucleotide, point mutation of specific residues within the ROMK2 phosphate loop (P-loop) were investigated. These either enhanced or attenuated the sensitivity to both activation and inhibition by Mg-ATP, thus demonstrating a direct interaction of nucleotide with the channel-forming polypeptide.
  • Published In

    Keywords

  • Adenosine Triphosphate, Amino Acid Sequence, Animals, Female, Kidney, Molecular Sequence Data, Mutagenesis, Site-Directed, Nucleotides, Oocytes, Patch-Clamp Techniques, Potassium Channels, Xenopus
  • Digital Object Identifier (doi)

    Author List

  • McNicholas CM; Yang Y; Giebisch G; Hebert SC
  • Start Page

  • F275
  • End Page

  • F285
  • Volume

  • 271
  • Issue

  • 2 Pt 2