Figure 1. Mpc3 is a highly regulated member of the yeast MPC gene family.

A, Amino acid sequence comparison of the yeast Mpc mitochondrial pyruvate carriers. Mpc2 and Mpc3 are 83% identical in the N-terminal 106 amino acids. Mpc1 is 28% identical to Mpc2 or Mpc3 in the N-terminal 116 amino acids. Putative transmembrane domains were identified using the TMpred tool at ch.EMBnet.org. B, Mpc3 abundance is activated by salt stress and diauxic shift. Yeast strains expressing the indicated TAP-tagged Mpc proteins from the endogenous promoters were used. Cells were subjected to osmotic stress (0.4 M NaCl) or shifted from glucose to glycerol medium for the indicated times. Mpc proteins were visualized by anti-PAP immunoblotting and compared to total protein loading. C, the relative distribution of Mpc proteins changes during adaptation to salt stress or non fermentative growth conditions. The individual Mpc protein levels were quantified as in (B) using cells continuously growing in normal medium (YPD), high salt medium (0.4 M NaCl) or glycerol medium (YPGlyc). The relative abundance of each Mpc protein was calculated under each growth condition. Data are shown as mean +/− standard deviation from three independent experiments. Mpc3 protein levels are significantly higher (p<0.05) as compared to Mpc1 or Mpc2 on glycerol medium according to the Students t-test.