An intersubunit salt bridge near the selectivity filter stabilizes the active state of Kir1.1.

ABSTRACT: ROMK (Kir1.1) potassium channels are closed by internal acidification with a pKa of 6.7 +/- 0.01 in 100 mM external K and a pKa of 7.0 +/- 0.01 in 1 mM external K. Internal acidification in 1 mM K (but not 100 mM K) not only closed the pH gate but also inactivated Kir1.1, such that realkalization did not restore channel activity until high K was returned to the bath. We identified a new putative intersubunit salt bridge (R128-E132-Kir1.1b) in the P-loop of the channel near the selectivity filter that affected the K sensitivity of the inactivation process. Mutation of either R128-Kir1.1b or E132-Kir1.1b caused inactivation in both 1 mM and 100 mM external K during oocyte acidification. However, 300 mM external K (but not 200 mM Na + 100 mM K) protected both E132Q and R128Y from inactivation

SUBMITTER: Sackin H 

PROVIDER: S-EPMC2726312 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature