Crystal structure of the C-terminal four-helix bundle of the potassium channel KCa3.1.
KCa3.1 (also known as SK4 or IK1) is a mammalian intermediate-conductance potassium channel that plays a critical role in the activation of T cells, B cells, and mast cells, effluxing potassium ions to maintain a negative membrane potential for influxing calcium ions. KCa3.1 shares primary sequence...
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Public Library of Science (PLoS)
2018-01-01
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| author | Tianyang Ji Senena Corbalán-García Stevan R Hubbard |
| author_facet | Tianyang Ji Senena Corbalán-García Stevan R Hubbard |
| author_sort | Tianyang Ji |
| collection | DOAJ |
| description | KCa3.1 (also known as SK4 or IK1) is a mammalian intermediate-conductance potassium channel that plays a critical role in the activation of T cells, B cells, and mast cells, effluxing potassium ions to maintain a negative membrane potential for influxing calcium ions. KCa3.1 shares primary sequence similarity with three other (low-conductance) potassium channels: KCa2.1, KCa2.2, and KCa2.3 (also known as SK1-3). These four homotetrameric channels bind calmodulin (CaM) in the cytoplasmic region, and calcium binding to CaM triggers channel activation. Unique to KCa3.1, activation also requires phosphorylation of a single histidine residue, His358, in the cytoplasmic region, which relieves copper-mediated inhibition of the channel. Near the cytoplasmic C-terminus of KCa3.1 (and KCa2.1-2.3), secondary-structure analysis predicts the presence of a coiled-coil/heptad repeat. Here, we report the crystal structure of the C-terminal coiled-coil region of KCa3.1, which forms a parallel four-helix bundle, consistent with the tetrameric nature of the channel. Interestingly, the four copies of a histidine residue, His389, in an 'a' position within the heptad repeat, are observed to bind a copper ion along the four-fold axis of the bundle. These results suggest that His358, the inhibitory histidine in KCa3.1, might coordinate a copper ion through a similar binding mode. |
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| institution | DOAJ |
| issn | 1932-6203 |
| language | English |
| publishDate | 2018-01-01 |
| publisher | Public Library of Science (PLoS) |
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| spelling | doaj-art-08c2e39af35a4064a99714b33c6defc22025-08-20T03:04:38ZengPublic Library of Science (PLoS)PLoS ONE1932-62032018-01-01136e019994210.1371/journal.pone.0199942Crystal structure of the C-terminal four-helix bundle of the potassium channel KCa3.1.Tianyang JiSenena Corbalán-GarcíaStevan R HubbardKCa3.1 (also known as SK4 or IK1) is a mammalian intermediate-conductance potassium channel that plays a critical role in the activation of T cells, B cells, and mast cells, effluxing potassium ions to maintain a negative membrane potential for influxing calcium ions. KCa3.1 shares primary sequence similarity with three other (low-conductance) potassium channels: KCa2.1, KCa2.2, and KCa2.3 (also known as SK1-3). These four homotetrameric channels bind calmodulin (CaM) in the cytoplasmic region, and calcium binding to CaM triggers channel activation. Unique to KCa3.1, activation also requires phosphorylation of a single histidine residue, His358, in the cytoplasmic region, which relieves copper-mediated inhibition of the channel. Near the cytoplasmic C-terminus of KCa3.1 (and KCa2.1-2.3), secondary-structure analysis predicts the presence of a coiled-coil/heptad repeat. Here, we report the crystal structure of the C-terminal coiled-coil region of KCa3.1, which forms a parallel four-helix bundle, consistent with the tetrameric nature of the channel. Interestingly, the four copies of a histidine residue, His389, in an 'a' position within the heptad repeat, are observed to bind a copper ion along the four-fold axis of the bundle. These results suggest that His358, the inhibitory histidine in KCa3.1, might coordinate a copper ion through a similar binding mode.https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0199942&type=printable |
| spellingShingle | Tianyang Ji Senena Corbalán-García Stevan R Hubbard Crystal structure of the C-terminal four-helix bundle of the potassium channel KCa3.1. PLoS ONE |
| title | Crystal structure of the C-terminal four-helix bundle of the potassium channel KCa3.1. |
| title_full | Crystal structure of the C-terminal four-helix bundle of the potassium channel KCa3.1. |
| title_fullStr | Crystal structure of the C-terminal four-helix bundle of the potassium channel KCa3.1. |
| title_full_unstemmed | Crystal structure of the C-terminal four-helix bundle of the potassium channel KCa3.1. |
| title_short | Crystal structure of the C-terminal four-helix bundle of the potassium channel KCa3.1. |
| title_sort | crystal structure of the c terminal four helix bundle of the potassium channel kca3 1 |
| url | https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0199942&type=printable |
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