Early changes in membrane potential of Saccharomyces cerevisiae induced by varying extracellular K^sup +^, Na^sup +^ or H^sup +^ concentrations

• Published in: Journal of bioenergetics and biomembranes Vol. 45; no. 6; p. 561
• Main Authors: Plásek, Jaromír, Gásková, Dana, Ludwig, Jost, Höfer, Milan
• Format: Journal Article
• Language: English
• Published: New York Springer Nature B.V 01.12.2013
• Subjects: Fluorescence; Membranes; Mutation; Plasma; Potassium
• ISSN: 0145-479X; 1573-6881
• DOI: 10.1007/s10863-013-9528-6

Recently we introduced a fluorescent probe technique that makes possible to convert changes of equilibrium fluorescence spectra of 3,3'-dipropylthiadicarbocyanine, diS-C^sub 3^(3), measured in yeast cell suspensions under defined conditions into underlying membrane potential differences, scaled in millivolts (Plasek et al. in J Bioenerg Biomembr 44: 559-569, 2012 ). The results presented in this paper disclose measurements of real early changes of plasma membrane potential induced by the increase of extracellular K^sup +^, Na^sup +^ and H^sup +^ concentration in S. cerevisiae with and without added glucose as energy source. Whereas the wild type and the [increment]tok1 mutant cells exhibited similar depolarization curves, mutant cells lacking the two Trk1,2 potassium transporters revealed a significantly decreased membrane depolarization by K^sup +^, particularly at lower extracellular potassium concentration [K^sup +^]^sub out^. In the absence of external energy source plasma membrane depolarization by K^sup +^ was almost linear. In the presence of glucose the depolarization curves exhibited an exponential character with increasing [K^sup +^]^sub out^. The plasma membrane depolarization by Na^sup +^ was independent from the presence of Trk1,2 transporters. Contrary to K^sup +^, Na^sup +^ depolarized the plasma membrane stronger in the presence of glucose than in its absence. The pH induced depolarization exhibited a fairly linear relationship between the membrane potential and the pH^sub o^ of cell suspensions, both in the wild type and the [Delta]trk1,2 mutant strains, when cells were energized by glucose. In the absence of glucose the depolarization curves showed a biphasic character with enhanced depolarization at lower pH^sub o^ values.[PUBLICATION ABSTRACT]