Question

What enables proteins destined for nuclear import to pass through the nuclear pore?

Choose one:
A. Their nuclear localization signal interacts with the unstructured meshwork of proteins lining the pore.
B. They are recognized by receptors that interact with repeated amino acid sequences in proteins lining the nuclear pore.
C. They are unfolded to allow them to snake through the meshlike network of proteins lining the nuclear pore.
D. Their nuclear localization signal interacts with the cytosolic fibrils that extend from the pore.
E. They promote the hydrolysis of GTP, which provides the energy needed for their transport.

Answer 1

Proteins with nuclear localization signals bind to nuclear transport receptors, allowing them to interact with nuclear pore fibrils and pass through the nuclear pore via active transport fueled by ATP hydrolysis.

Step-by-step explanation:

The proteins destined for nuclear import pass through the nuclear pore due to the presence of nuclear localization signals (NLS). These signals are rich in positively charged amino acids, such as lysine and arginine, which enable the protein to bind to the nuclear transport receptors in the cytosol. Once bound, the receptor-protein complex approaches the nuclear pore and interacts with the nuclear pore fibrils, subsequently causing the pore to open. This allows the complex to pass through the double membrane of the nuclear envelope. The process of nuclear import is active transport, which is fueled by ATP hydrolysis to move proteins against a concentration gradient into the nucleus.