Random mutagenesis screening indicates the absence of a separate H(+)-sensor in the pH-sensitive Kir channels.
Several inwardly-rectifying (Kir) potassium channels (Kir1.1, Kir4.1 and Kir4.2) are characterised by their sensitivity to inhibition by intracellular H(+) within the physiological range. The mechanism by which these channels are regulated by intracellular pH has been the subject of intense scrutiny...
| Main Authors: | , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
2010
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| _version_ | 1826295204960796672 |
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| author | Paynter, J Shang, L Bollepalli, M Baukrowitz, T Tucker, S |
| author_facet | Paynter, J Shang, L Bollepalli, M Baukrowitz, T Tucker, S |
| author_sort | Paynter, J |
| collection | OXFORD |
| description | Several inwardly-rectifying (Kir) potassium channels (Kir1.1, Kir4.1 and Kir4.2) are characterised by their sensitivity to inhibition by intracellular H(+) within the physiological range. The mechanism by which these channels are regulated by intracellular pH has been the subject of intense scrutiny for over a decade, yet the molecular identity of the titratable pH-sensor remains elusive. In this study we have taken advantage of the acidic intracellular environment of S. cerevisiae and used a K(+) -auxotrophic strain to screen for mutants of Kir1.1 with impaired pH-sensitivity. In addition to the previously identified K80M mutation, this unbiased screening approach identified a novel mutation (S172T) in the second transmembrane domain (TM2) that also produces a marked reduction in pH-sensitivity through destabilization of the closed-state. However, despite this extensive mutagenic approach, no mutations could be identified which removed channel pH-sensitivity or which were likely to act as a separate H(+) -sensor unique to the pH-sensitive Kir channels. In order to explain these results we propose a model in which the pH-sensing mechanism is part of an intrinsic gating mechanism common to all Kir channels, not just the pH-sensitive Kir channels. In this model, mutations which disrupt this pH-sensor would result in an increase, not reduction, in pH-sensitivity. This has major implications for any future studies of Kir channel pH-sensitivity and explains why formal identification of these pH-sensing residues still represents a major challenge. |
| first_indexed | 2024-03-07T03:57:27Z |
| format | Journal article |
| id | oxford-uuid:c359f68c-1997-4a15-8f3c-84d874733649 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T03:57:27Z |
| publishDate | 2010 |
| record_format | dspace |
| spelling | oxford-uuid:c359f68c-1997-4a15-8f3c-84d8747336492022-03-27T06:15:52ZRandom mutagenesis screening indicates the absence of a separate H(+)-sensor in the pH-sensitive Kir channels.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:c359f68c-1997-4a15-8f3c-84d874733649EnglishSymplectic Elements at Oxford2010Paynter, JShang, LBollepalli, MBaukrowitz, TTucker, SSeveral inwardly-rectifying (Kir) potassium channels (Kir1.1, Kir4.1 and Kir4.2) are characterised by their sensitivity to inhibition by intracellular H(+) within the physiological range. The mechanism by which these channels are regulated by intracellular pH has been the subject of intense scrutiny for over a decade, yet the molecular identity of the titratable pH-sensor remains elusive. In this study we have taken advantage of the acidic intracellular environment of S. cerevisiae and used a K(+) -auxotrophic strain to screen for mutants of Kir1.1 with impaired pH-sensitivity. In addition to the previously identified K80M mutation, this unbiased screening approach identified a novel mutation (S172T) in the second transmembrane domain (TM2) that also produces a marked reduction in pH-sensitivity through destabilization of the closed-state. However, despite this extensive mutagenic approach, no mutations could be identified which removed channel pH-sensitivity or which were likely to act as a separate H(+) -sensor unique to the pH-sensitive Kir channels. In order to explain these results we propose a model in which the pH-sensing mechanism is part of an intrinsic gating mechanism common to all Kir channels, not just the pH-sensitive Kir channels. In this model, mutations which disrupt this pH-sensor would result in an increase, not reduction, in pH-sensitivity. This has major implications for any future studies of Kir channel pH-sensitivity and explains why formal identification of these pH-sensing residues still represents a major challenge. |
| spellingShingle | Paynter, J Shang, L Bollepalli, M Baukrowitz, T Tucker, S Random mutagenesis screening indicates the absence of a separate H(+)-sensor in the pH-sensitive Kir channels. |
| title | Random mutagenesis screening indicates the absence of a separate H(+)-sensor in the pH-sensitive Kir channels. |
| title_full | Random mutagenesis screening indicates the absence of a separate H(+)-sensor in the pH-sensitive Kir channels. |
| title_fullStr | Random mutagenesis screening indicates the absence of a separate H(+)-sensor in the pH-sensitive Kir channels. |
| title_full_unstemmed | Random mutagenesis screening indicates the absence of a separate H(+)-sensor in the pH-sensitive Kir channels. |
| title_short | Random mutagenesis screening indicates the absence of a separate H(+)-sensor in the pH-sensitive Kir channels. |
| title_sort | random mutagenesis screening indicates the absence of a separate h sensor in the ph sensitive kir channels |
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