Salt bridges in the miniature viral channel Kcv are important for function
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The viral potassium channel Kcv comprises only 94 amino acids, which represent the pore module of more complex K+ channels. As for Kir-type channels, Kcv also has a short N-terminal helix exposed to the cytoplasm, upstream of the first transmembrane domain. Here we show that this helix is relevant for Kcv function. The presence of charged amino acids, which form dynamic inter- and intra-subunit salt bridges is crucial. Electrophysiological measurements, yeast rescue experiments and molecular dynamics simulations show that mutants in which the critical salt bridge formation is impaired have no or reduced channel activity. We conclude that these salt bridges destabilise the complexation of K+ ions by negative charges on the inner transmembrane domain at the entrance into the cavity. This feature facilitates a continuous and coordinated transfer of ions between the cavity and the cytoplasm for channels without the canonical bundle crossing.
KeywordsSalt bridge Kcv-channel Channel gating K+ channel MD simulation
List of abbreviations
Green fluorescent protein
This work was supported in part by the Deutsche Forschungsgemeinschaft (to G. T. and S. M. K), GrK1114 (to G.T.), Fonds der Chemischen Industrie (to S. M. K.) the Adolf-Messer-Stiftung (to S. M. K.) and the European Drug Initiative on Channels and Transporters (EDICT) project EU FP7 (201924) to A.M. We are grateful to D. Herten and P. Heinlein for help with microscopy (Bioquant, Heidelberg). Computer time was provided on IBM Regatta systems at the Hochschulrechenzentrum Darmstadt and at the Forschungszentrum Jülich. Yeast strains were generously provided by Dr. D. Minor (UCSF).
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