Question

You are going to measure the import of a protein into mitochondria in the in vitro assay. You add a drug that inhibits the electron transport chain. Which of the following will be a likely effect of adding this drug?

1) The MTS of the protein will not bind to the TOM receptor
2) Cytosolic Hsp70 will not bind to the protein
3) The MTS of the protein will not pass through the TOM channel
4) The MTS of the protein will not pass through the TIM channel
5) The protein will reach the Matrix but will not be cleaved by the signal peptidase

Answer 1

Inhibiting the electron transport chain will likely result in the option 5) protein reaching the mitochondrial matrix but not being cleaved by the signal peptidase due to the lack of ATP needed for this step.

Step-by-step explanation:

If you add a drug that inhibits the electron transport chain in mitochondria, the likely effect on the import of a protein into mitochondria would be that the protein reaches the matrix but will not be cleaved by the signal peptidase, option 5) is correct answer. This is because the drug would interrupt the proton gradient that is necessary for generating ATP through oxidative phosphorylation. Without adequate levels of ATP, which is required for the energy-dependent steps in protein import, the protein may still be able to pass through the TOM and TIM channels, given that these processes may not be directly energy-dependent. However, the final maturation steps such as the cleavage by signal peptidase and proper folding, which do require ATP, would likely be compromised.