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TbIRK is a signature sequence free potassium channel from Trypanosoma brucei locating to acidocalcisomes

Steinmann, Michael E. and Schmidt, Remo S. and Bütikofer, Peter and Mäser, Pascal and Sigel, Erwin. (2017) TbIRK is a signature sequence free potassium channel from Trypanosoma brucei locating to acidocalcisomes. Scientific Reports, 7 (1). p. 656.

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Abstract

Potassium channels from prokaryotes and eukaryotes are usually recognized by a typical amino acid sequence TXTGY(F)G representing the ionic selectivity filter. Using a screening approach with ion channel family profiles but without the above motif, we identified a gene in Trypanosoma brucei that exhibits homology to inward rectifying potassium channels. We report here cloning of this ion channel named TbIRK. The protein is localized to acidocalcisomes in procyclic and in bloodstream form parasites. Functional properties of this channel were established after expression in Xenopus oocytes. Currents recorded in potassium medium show inward rectification and little time dependence. Surprisingly, this channel retains selectivity for potassium ions over sodium ions >7, in spite of the lack of the classical selectivity filter. The sequence GGYVG was predicted in silico to replace this filter motif. Point mutations of the corresponding glycine residues confirmed this at the functional level. The channel is inhibited by caesium ions but remains unaffected by barium ions up to 10 mM. TbIRK is to our knowledge the first potassium channel in T. brucei that localizes to the acidocalcisomes, organelles involved in the storage of phosphates and the response to osmotic stress that occurs during the life cycle of trypanosomes.
Faculties and Departments:09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Medical Parasitology and Infection Biology (MPI) > Parasite Chemotherapy (Mäser)
UniBasel Contributors:Mäser, Pascal
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Nature Publishing Group
e-ISSN:2045-2322
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:12 Oct 2017 09:51
Deposited On:29 May 2017 12:46

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