Membrane Biology
Control of KirBac3.1 Potassium Channel Gating at the Interface between Cytoplasmic Domains*

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KirBac channels are prokaryotic homologs of mammalian inwardly rectifying potassium (Kir) channels, and recent structures of KirBac3.1 have provided important insights into the structural basis of gating in Kir channels. In this study, we demonstrate that KirBac3.1 channel activity is strongly pH-dependent, and we used x-ray crystallography to determine the structural changes that arise from an activatory mutation (S205L) located in the cytoplasmic domain (CTD). This mutation stabilizes a novel energetically favorable open conformation in which changes at the intersubunit interface in the CTD also alter the electrostatic potential of the inner cytoplasmic cavity. These results provide a structural explanation for the activatory effect of this mutation and provide a greater insight into the role of the CTD in Kir channel gating.

Crystal Structure
Ion Channels
Membrane Proteins
Molecular Dynamics
Potassium Channels
Channel Gating
Kir Channel
KirBac

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*

This work was supported, in whole or in part, by the National Institute of Health Grant HL54171 (to C. G. N.). This work was also supported by grants from the Biotechnology and Biological Sciences Research Council (to S. J. T. and C. V.-B.) and the Wellcome Trust (to M. S. P. S.).

The atomic coordinates and structure factors (code 4LP8) have been deposited in the Protein Data Bank (http://wwpdb.org/).

1

Both authors contributed equally to this work.

2

Birmingham University Fellow.