Final answer:
The nuclear transport receptor protein, or importin, binds to nuclear localization signals on proteins, allowing them to enter the nucleus through the nuclear pore complex with the energy provided by ATP hydrolysis.
Step-by-step explanation:
The nuclear transport receptor protein, known as importin, specifically binds to nuclear localization signals (NLS) on proteins that are destined for the nucleus.
These signals typically contain a sequence rich in positively charged amino acids like lysine and arginine, which enable interaction with the negatively charged domain of the importin.
This complex then approaches the nuclear pore complex (NPC) where it interacts with fibrils to allow the protein to enter the nucleus. The energy for this active transport is provided by ATP hydrolysis.