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GCN4 enhances the stability of the pore domain of potassium channel KcsA
Author(s) -
Yuchi Zhiguang,
Pau Victor P. T.,
Yang Daniel S. C.
Publication year - 2008
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06747.x
Subject(s) - kcsa potassium channel , potassium channel , potassium , stability (learning theory) , domain (mathematical analysis) , biophysics , chemistry , ion channel , computer science , mathematics , biology , biochemistry , mathematical analysis , receptor , organic chemistry , machine learning
The prokaryotic potassium channel from Streptomyces lividans , KcsA, is the first channel that has a known crystal structure of the transmembrane domain. The crystal structure of its soluble C‐terminal domain, however, still remains elusive. Biophysical and electrophysiological studies have previously implicated the essential roles of the C‐terminal domain in pH sensing and in vivo channel assembly. We examined this functional assignment by replacing the C‐terminal domain with an artificial tetramerization domain, GCN4‐LI. The expression of KcsA is completely abolished when its C‐terminal domain is deleted, but it can be rescued by fusion with GCN4‐LI. The secondary and quaternary structures of the hybrid channel are very similar to those of the wild‐type channel according to CD and gel‐filtration analyses. The thermostability of the hybrid channel at pH 8 is similar to that of the wild‐type but is insensitive to pH changes. This supports the notion that the pH sensor of KcsA is located in the C‐terminal domain. The result obtained in the present study is in agreement with the proposed functions of the C‐terminal domain and we show that the channel assembly role of the C‐terminal domain can be substituted with a non‐native tetrameric motif. Because tetramerization domains are found in different families of potassium channels and their presence often enhances the expression of channels, replacement of the elusive C‐terminal domains with a known tetrameric scaffold could potentially assist the expression of other potassium channels.