1.A.88 The Fungal Potassium Channel (F-Kch) Family 

In the budding yeast Saccharomyces cerevisiae, mating pheromones activate a high-affinity Ca2+ influx system (HACS) that activates calcineurin and is essential for cell survival. Stefan et al. 2013 identified extracellular K+ and a homologous pair of transmembrane proteins, Kch1 and Kch2 (Prm6), as necessary components of the HACS activation mechanism. Expression of Kch1 and especially Kch2 was strongly induced during the response to mating pheromones. When forcibly overexpressed, Kch1 and Kch2 localized to the plasma membrane and activated HACS in a fashion that depended on extracellular K+ but not pheromones. They also promoted growth of trk1 trk2 mutant cells in low K+ environments, suggesting that they promote K+ uptake. Voltage-clamp recordings of protoplasts revealed diminished inward K+ currents in kch1 kch2 double-mutant cells relative to the wild type. Conversely, heterologous expression of kch1 in HEK293T cells caused the appearance of inwardly rectifying K+ currents. Collectively, these findings suggest that Kch1 and Kch2 directly promote K+ influx and that HACS may electrochemically respond to K+ influx in much the same way as the homologous voltage-gated Ca2+ channels in most animal cell types (Stefan et al. 2013).


 

References:

Stefan, C.P., N. Zhang, T. Sokabe, A. Rivetta, C.L. Slayman, C. Montell, and K.W. Cunningham. (2013). Activation of an essential calcium signaling pathway in Saccharomyces cerevisiae by Kch1 and Kch2, putative low-affinity potassium transporters. Eukaryot. Cell. 12: 204-214.

Examples:

TC#NameOrganismal TypeExample
1.A.88.1.1

K+ channel, Kch1 of 497 aas (Stefan et al. 2013).

Fungi

Kch1 of Saccharomyes cerevisiae

 
1.A.88.1.2

K+ channel Kch2/Pmp6 of 352 aas (Stefan et al. 2013).

Fungi

Kch2 of Saccharomyces cerevisiae

 
1.A.88.1.3

Kch homologue of 655 aa

Fungi

Kch homologue of Candida maltosa

 
1.A.88.1.4

Kch homologue of 1043 aas

Fungi

Kch homologue of Aspergillus niger

 
1.A.88.1.5

Vacuolar Kch homologue of 422 aas

Fungi

Kch of Cryptococcus (Filobasidiella) gattii (bacillisporus)

 
1.A.88.1.6

Kch homologue of 1090 aas

Fungi

Kch of Neurospora crassa

 
1.A.88.1.7

Vacuolar Kch homologue of 527 aas

Fungi

Kch of Trichosporon asahii

 
1.A.88.1.8

Kch homologue of 442 aas

Fungi

Kch of Dekkera bruxellensis

 
1.A.88.1.9

Kch homologue of 565 aas

Fungi

Kch of Millerozyma (Pichia) farinosa (sorbitophila