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Multiple residues in the P-region and M2 of murine Kir 2.1 regulate blockage by external Ba2+
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Lee, Young Mee, Thompson, Gareth A., Ashmole, I., Leyland, Mark, So, Insuk and Stanfield, Peter R. (2009) Multiple residues in the P-region and M2 of murine Kir 2.1 regulate blockage by external Ba2+. Korean Journal of Physiology & Pharmacology, Vol.13 (No.1). pp. 61-70. doi:10.4196/kjpp.2009.13.1.61 ISSN 1226-4512.
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Official URL: http://dx.doi.org/10.4196/kjpp.2009.13.1.61
Abstract
We have examined the effects of certain mutations of the selectivity filter and of the membrane helix M2 on Ba2+ blockage of the inward rectifier potassium channel, Kir 2.1. We expressed mutant and wild type murine Kir 2.1 in Chinese hamster ovary (CHO) cells and used the whole cell patch-clamp technique to record K+ currents in the absence and presence of externally applied Ba2+. Wild type Kir2.1 was blocked by externally applied Ba2+ in a voltage and concentration dependent manner. Mutants of Y145 in the selectivity filter showed little change in the kinetics of Ba2+ blockage. The estimated K-d(0) was 108 mu M for Kir2.1 wild type, 124 mu M for a concatameric WT-Y145V dimer, 109 mu M for a WT-Y145L dimer, and 267 mu M for Y145F. Mutant channels T141A and S165L exhibit a reduced affinity together with a large reduction in the rate of blockage. In S165L, blockage proceeds with a double exponential time course, suggestive of more than one blocking site. The double mutation T141A/S165L dramatically reduced affinity for Ba2+, also showing two components with very different time courses. Mutants D172K and D172R (lining the central, aqueous cavity of the channel) showed both a decreased affinity to Ba2+ and a decrease in the on transition rate constant (k(on)). These results imply that residues stabilising the cytoplasmic end of the selectivity filter (T141, S165) and in the central cavity (D172) are major determinants of high affinity Ba2+ blockage in Kir 2.1.
| Item Type: | Journal Article | ||||
|---|---|---|---|---|---|
| Subjects: | R Medicine > RS Pharmacy and materia medica Q Science > QP Physiology |
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| Divisions: | Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) > Biological Sciences ( -2010) | ||||
| Journal or Publication Title: | Korean Journal of Physiology & Pharmacology | ||||
| Publisher: | Korean Society of Pharmacology | ||||
| ISSN: | 1226-4512 | ||||
| Official Date: | February 2009 | ||||
| Dates: |
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| Volume: | Vol.13 | ||||
| Number: | No.1 | ||||
| Number of Pages: | 10 | ||||
| Page Range: | pp. 61-70 | ||||
| DOI: | 10.4196/kjpp.2009.13.1.61 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access | ||||
| Funder: | Wellcome Trust, SNU, BK21 Human Life Science | ||||
| Grant number: | 800-20000229, 800-20000125 |
Data sourced from Thomson Reuters' Web of Knowledge
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