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. 2014 Jun 6;9(6):e98969. doi: 10.1371/journal.pone.0098969

Figure 4. Model of GDP and GTP action in mitochondria.

Figure 4

Extramitochondrial GDP can be transphosphorylated to GTP in the presence of ATP in a reaction catalyzed by mitochondrial NDPK. NDPK is bound to the cytosolic-facing or matrix-facing IMM leaflet but is shown separately for clarity. Alternatively, extramitochondrial GDP can be imported via ANT or another, as-yet-unknown, CATR-sensitive carrier into the mitochondrial matrix to enable its OXPHOS. In turn, extramitochondrial GTP, or GTP synthesized in the NDPK-dependent reaction, functions as the stronger UCP inhibitor (blunt-end solid arrow) than GDP (blunt-end dashed arrow).