Referenced in: none

Automatically associated channels: Kir1.1 , Kir2.1

Title: Identification of a titratable lysine residue that determines sensitivity of kidney potassium channels (ROMK) to intracellular pH.

Authors: B Fakler, J H Schultz, J Yang, U Schulte, U Brandle, H P Zenner, L Y Jan, J P Ruppersberg

Journal, date & volume: EMBO J., 1996 Aug 15 , 15, 4093-9

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/8861938

Abstract
Potassium (K+) homeostasis is controlled by the secretion of K+ ions across the apical membrane of renal collecting duct cells through a low-conductance inwardly rectifying K+ channel. The sensitivity of this channel to intracellular pH is particularly high and assumed to play a key role in K+ homeostasis. Recently, the apical K+ channel has been cloned (ROMK1,2,3 = Kir1.1a, Kir1.1b and Kir1.1c) and the pH dependence of ROMK1 was shown to resemble closely that of the native apical K+ channel. It is reported here that the steep pH dependence of ROMK channels is determined by a single amino acid residue located in the N-terminus close to the first hydrophobic segment M1. Changing lysine (K) at position 80 to methionine (M) removed the sensitivity of ROMK1 channels to intracellular pH. In pH-insensitive IRK1 channels, the reverse mutation (M84K) introduced dependence on intracellular pH similar to that of ROMK1 wild-type. A detailed mutation analysis suggests that a shift in the apparent pKalpha of K80 underlies the pH regulation of ROMK1 channels in the physiological pH range.