Question

SNARE proteins are found in the membranes of all of the following compartments EXCEPT

A. Mitochondria
B. Binding of SRP to an N-terminal signal sequence
C. Binding of their mRNAs to a special class of ribosomes attached to the ER

Answer 1

SNARE proteins are not found in mitochondria because mitochondrial protein transfer occurs post-translationally, unlike the co-translational packaging of proteins by the RER that involves SNARE-mediated vesicular trafficking.

Step-by-step explanation:

The SNARE proteins are involved in the fusion of vesicles with target membranes within a cell. They are primarily recognized in the context of the endomembrane system which includes the RER (rough endoplasmic reticulum), the Golgi apparatus, and the plasma membrane, among others. SNARE proteins do not typically associate with mitochondria, as mitochondrial protein transfer is post-translational. Mitochondrial proteins have N-terminal signal peptides that bind to receptors on the mitochondrial membrane. This is in contrast to the co-translational packaging of proteins by the RER, which is mediated by SNARE proteins involved in the trafficking of vesicles through the endomembrane system.