From the Research
The answer is "A slight, short-term increase in oxygen consumption, followed by no oxygen consumption." Atractyloside inhibits the adenine nucleotide translocase (ANT), which is responsible for exchanging ADP from the cytosol with ATP from the mitochondrial matrix. When atractyloside is present, ADP cannot enter the mitochondrial matrix, preventing ATP synthesis via oxidative phosphorylation.
Key Points:
- Initially, there might be a brief increase in oxygen consumption as the electron transport chain begins to function with the available substrates (pyruvate) 1.
- However, this consumption would quickly cease because without ADP entry into the matrix, the F1F0 ATP synthase cannot operate, causing protons to accumulate in the intermembrane space.
- This proton buildup creates a strong electrochemical gradient that inhibits further electron transport and oxygen consumption, as described in the regulation of oxidative phosphorylation 1.
- The system essentially stalls due to the inability to dissipate the proton gradient through ATP synthesis, highlighting the crucial role of ANT in mitochondrial function 2.
Mechanism:
- The mitochondrial ADP/ATP carrier plays a vital role in transporting ADP into the mitochondrial matrix for ATP synthesis, and ATP out to fuel the cell 2.
- Atractyloside binds to the ADP/ATP-binding site, preventing the carrier from cycling between cytoplasmic-open and matrix-open states, and thus inhibiting ADP transport into the matrix.
- The inhibition of ADP transport leads to a decrease in ATP synthesis, which in turn affects the energy state of the cell, as discussed in the context of oxidative phosphorylation regulation 1.