Question

Certain cysteine-containing proteins of the mitochondrial intermembrane space are imported from the cytosol with the help of the Mia40 protein via a disulfide relay system. What drives the unidirectional import of these proteins? Are these proteins reduced or oxidized at their cysteine residues upon import?

A. ATP hydrolysis; oxidized
B. The electron-transport chain; oxidized
C. ATP hydrolysis; neither oxidized nor reduced
D. ATP hydrolysis; reduced
E. The electron-transport chain; reduced

Answer 1

The unidirectional import of cysteine-containing proteins into the mitochondrial intermembrane space via the Mia40 protein is driven by the formation of disulfide bonds, causing these proteins to be oxidized upon import.

Step-by-step explanation:

The Mia40 protein facilitates the import of cysteine-containing proteins into the mitochondrial intermembrane space through a disulfide relay system. The unidirectional import of these proteins is driven by their oxidation within the intermembrane space, not by ATP hydrolysis or the electron-transport chain. This oxidation process generates disulfide bonds within the cysteine residues of the imported proteins, hence they are in an oxidized state upon import.