Identification of a titratable lysine residue that determines sensitivity of kidney potassium channels (ROMK) to intracellular pH.
AUTOR(ES)
Fakler, B
RESUMO
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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=452131Documentos Relacionados
- The effect of intracellular pH on ATP-dependent potassium channels of frog skeletal muscle.
- Effects of intracellular pH on calcium-activated potassium channels in rabbit tracheal smooth muscle.
- Microinjection of ras p21 induces a rapid rise in intracellular pH.
- Titratable acidity of beverages influences salivary pH recovery
- Potassium/proton antiport system of growing Enterococcus hirae at high pH.