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The role of a single aspartate residue in ionic selectivity and block of a murine inward rectifier K+ channel Kir2.1.
Author(s) -
Abrams C J,
Davies N W,
Shelton P A,
Stanfield P R
Publication year - 1996
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1996.sp021411
Subject(s) - inward rectifier potassium ion channel , chemistry , selectivity , hyperpolarization (physics) , biophysics , protein subunit , potassium channel , mutant , wild type , ion channel , blocking effect , stereochemistry , biochemistry , receptor , biology , psychology , developmental psychology , nuclear magnetic resonance spectroscopy , gene , catalysis
1. The effects of Rb+ and Cs+ as blocking ions were investigated on wild‐type and mutant forms of the inward rectifier K+ channel, IRK1 (Kir2.1). 2. In wild‐type channels, Rb+ blockage was voltage dependent, increasing and then falling with increasing hyperpolarization. 3. Rb+ blockage was abolished by replacing Asp172 in the M2 domain of the pore‐forming subunit by Asn, but was re‐established by a change to Gln, narrowing the pore. Blocking affinity was reduced in D172Q, and was also reduced by replacing Gly168 in M2 by Ala. 4. Cs+ blockage was also abolished in D172N but was re‐established in D172Q. 5. There appears to be a balance between charge and pore size in determining whether ions block or permeate. A major part of the selectivity of Kir2.1 is associated with Asp172 in the M2 domain.