Final answer:
Proteins transported across the NPC are in an active state and require energy. They undergo conformational changes and interact with carrier proteins to cross the nuclear envelope and enter the nucleus.
Step-by-step explanation:
The proteins transported across the NPC (nuclear pore complex) are in an active state. The process of transporting proteins across the NPC requires energy in the form of ATP hydrolysis. The proteins undergo conformational changes and interact with carrier proteins to cross the nuclear envelope and enter the nucleus.