pH of media of COS7 cells transfected with different PLP1 constructs. Non-transfected and EGFP transfected COS7 cells have normal pH values of 8.0 and 7.9, respectively. COS7 cells transfected with C6SPlp1EGFP and C10SPlp1EGFP, which prevent insertion of PLP into mitochondria, have pH values of 7.9, identical to non-transfected COS7 cells. In contrast, COS7 cells transfected with a wtPLP1EGFP and C7APlp1HA cDNAs, which permit insertion into mitochondria, have a pH of 7.4. The pH measurement for each cell group is based upon 2-4 different experiments with 4-8 wells measured for each group. Two-tailed T-test between nontransfected and transfected groups. Error bars are SD.