Ist2 in the Yeast Cortical Endoplasmic Reticulum Promotes Trafficking of the Amino Acid Transporter Bap2 to the Plasma Membrane
Figure 2
H+ gradients across the ER membrane depend on transition to respiration.
(A) Cartoon illustrating the localization of compartment-specific pH probes. pH-T78C and pH-T8C exclusively localize to the cortical ER while Get2-pH and pH-Get2 localize to the general ER. (B) In vivo measurement of cytosolic pH in cells grown for 12 to 27 hours in HC medium lacking leucine. Growth phases (fermentative, transition and respiratory) are indicated. WT cells expressing pHluorin (black squares) or pH-Get2 (blue triangles) were analyzed by flow cytometry. Error bars indicate s.d.m. (n = 2). (C) pH in the cytosol (black) and general ER lumen (grey) of WT (filled bars) and ist2Δ (open bars) cells expressing pH-Get2 and Get2-pH under fermentative and respiratory conditions. Error bars indicate s.d.m. (n = 4). (D) H+ gradients (mol/L) between cytosol and lumen of the general (black) or cortical (grey) ER in WT (filled bars) and ist2Δ (open bars) cells under fermentative and respiratory conditions. The H+ concentrations of general and cortical ER cells were determined in cells expressing Get2-pH and pH-T8C, respectively. Cytosolic H+ concentrations in the vicinity of general and cortical ER were determined in cells expressing pH-Get2 and pH-T7C, respectively. Error bars indicate s.d.m. (n = 4).