FIGURE 6.

Functionality of CAX1 and CAX3 when co-expressed with CAX half proteins. A, suppression of Li⁺, Na⁺, and Ca²⁺ sensitivity of K667 yeast cells expressing sCAX1, CAX1, or CAX3, or co-expressing CAX1 with sCAX1 N-terminal half protein (N-sCAX1), CAX1 C-terminal half protein (C-CAX1), sCAX3 N-terminal half protein (N-sCAX3), CAX3 C-terminal half protein (C-CAX3), or CAX1H338N C-terminal half protein (C-H338N). Saturated liquid cultures of K667 yeast were diluted in stepwise 5-fold dilutions and then spotted onto selection medium or YPD medium containing either 150 mm CaCl₂, 100 mm LiCl, or 600 mm NaCl. Yeast cells expressing empty vector were used as a negative control. The plates were incubated and photographed after 2 days at 30 °C. B, Li⁺, Na⁺, and Ca²⁺ ion content analysis in K667 yeast cells co-expressing sCAX1 or CAX1 with vector or CAX1 in combination with N-sCAX1, C-CAX1, N-sCAX3, C-CAX3, or C-H338N grown to stationary phase in YPD medium supplemented with 500 μm LiCl (for the Li⁺ and Na⁺ content measurements) or 10 mm CaCl₂ (for the Ca²⁺ content measurements). The data from five repeats were calculated with a formula: (Ion_cax − Ion_vector)/Ion_vector × 100, and expressed as the means ± S.E. (n = 5). As discussed previously, the ion content fluctuated depending on the growth medium used.