Residues at the outer mouth of Kir1.1 determine K-dependent gating. Academic Article uri icon

Overview

abstract

  • Three residues (E132, F127, and R128) at the outer mouth of Kir1.1b directly affected inward rectifier gating by external K, independent of pH gating. Each of the individual mutations E132Q, F127V, F127D, and R128Y changed the normal K dependence of macroscopic conductance from hyperbolic (Km = 6 ± 2 mM) to linear, up to 500 mM, without changing the hyperbolic K dependence of single-channel conductance. This suggests that E132, F127, and R128 are responsible for maximal Kir1.1b activation by external K. In addition, these same residues were also essential for recovery of Kir1.1b activity after complete removal of external K by 18-Crown-6 polyether. In contrast, charge-altering mutations at neighboring residues (E92A, E104A, D97V, or Q133E) near the outer mouth of the channel did not affect Kir1.1b recovery after chelation of external K. The collective role of E132, R128, and F127 in preventing Kir1.1b inactivation by either cytoplasmic acidification or external K removal implies that pH inactivation and the external K sensor share a common mechanism, whereby E132, R128, and F127 stabilize the Kir1.1b selectivity filter gate in an open conformation, allowing rapid recovery of channel activity after a period of external K depletion.

publication date

  • June 19, 2012

Research

keywords

  • Ion Channel Gating
  • Potassium
  • Potassium Channels, Inwardly Rectifying

Identity

PubMed Central ID

  • PMC3379619

Scopus Document Identifier

  • 84862654925

Digital Object Identifier (DOI)

  • 10.1016/j.bpj.2012.05.018

PubMed ID

  • 22735524

Additional Document Info

volume

  • 102

issue

  • 12