We studied block of the internal pore of the ROMK1 inward-rectifier K+ channel by Mg2+ and five quaternary ammoniums (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and tetrapentylammonium). The apparent affinity of these blockers varied as a function of membrane voltage. As a consequence, the channel conducted K+ current more efficiently in the inward than the outward direction; i.e., inward rectification. Although the size of some monovalent quaternary ammoniums is rather large, the zδ values (which measure voltage dependence of their binding to the pore) were near unity in symmetric 100 mM K+. Furthermore, we observed that not only the apparent affinities of the blockers themselves, but also their dependence on membrane voltage (or zδ), varied as a function of the concentration of extracellular K+. These results suggest that there is energetic coupling between the binding of blocking and permeating (K+) ions, and that the voltage dependence of channel blockade results, at least in part, from the movement of K+ ions in the electrical field. A further quantitative analysis of the results explains why the complex phenomenon of inward rectification depends on both membrane voltage and the equilibrium potential for K+.
Skip Nav Destination
Article navigation
1 August 1998
Article|
August 01 1998
Coupled Ion Movement Underlies Rectification in an Inward-Rectifier K+ Channel
Maria Spassova,
Maria Spassova
From the Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
Search for other works by this author on:
Zhe Lu
Zhe Lu
From the Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
Search for other works by this author on:
Maria Spassova
From the Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
Zhe Lu
From the Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
Address correspondence to Dr. Zhe Lu, University of Pennsylvania, Department of Physiology, D302A Richards Building, 3700 Hamilton Walk, Philadelphia, PA 19104-6085. Fax: 215-573-5851; E-mail: [email protected]
Received:
February 27 1998
Accepted:
March 08 1998
Online ISSN: 1540-7748
Print ISSN: 0022-1295
1998
J Gen Physiol (1998) 112 (2): 211–221.
Article history
Received:
February 27 1998
Accepted:
March 08 1998
Citation
Maria Spassova, Zhe Lu; Coupled Ion Movement Underlies Rectification in an Inward-Rectifier K+ Channel . J Gen Physiol 1 August 1998; 112 (2): 211–221. doi: https://doi.org/10.1085/jgp.112.2.211
Download citation file:
Sign in
Don't already have an account? Register
Client Account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Sign in via your Institution
Sign in via your InstitutionSuggested Content
Tuning the Voltage Dependence of Tetraethylammonium Block with Permeant Ions in an Inward-Rectifier K+ Channel
J Gen Physiol (September,1999)
Potassium-dependent Changes in the Conformation of the Kv2.1 Potassium Channel Pore
J Gen Physiol (June,1999)
Email alerts
Advertisement