Figure 6. Wildtype but not an active site mutant PTPMT1 rescues cardiolipin deficiency.

A) The expression of β-galactosidase (LacZ), wildtype PTPMT1 (MT1), or catalytically inactive PTPMT1 mutant (CS). B) After labeling MEFs with ³²P-orthophosphate, phospholipids were extracted and the percentage of cardiolipin (CL) among total phospholipids was determined by TLC analysis. Mean ± S.E.M. from three independent experiments, one-way ANOVA with a post hoc F test, ***p<0.001, **p<0.01. C) The accumulation of PGP in Ptpmt1-deficient cells. For each sample, 50,000cpm of ³²P-labeled phospholipids were applied onto TLC plates and visualized by phosphoimager. D) Oxygen consumption rates of intact MEFs cultured in regular medium. The basal rate, the State 4 rate (Oligo), and the maximal uncoupler stimulated rate (FCCP) are shown as described in Figure 2. Mean ± SEM from four replicates. E) Wildtype but not mutant PTPMT1 complements the growth deficiency of yeast PGP phosphatase GEP4-null (gep4Δ) cells in a serial dilution spotting assay. The expression levels of FLAG-tagged GEP4 and PTPMT1 are indicated by western blot analysis. The level of CDC2 is shown as control. WT, wildtype strain. (−) empty vector. SCD, synthetic complete medium with dextrose. EtBr, Ethidium Bromide. See also Figure S4 and Table S1.