Final answer:
The cargo exhibits a nuclear localization signal rich in positively charged amino acids for protein import into the nucleus. This signal facilitates binding to nuclear transport receptors and passage through nuclear pores using energy from ATP hydrolysis.
Step-by-step explanation:
The signal exhibited by cargo during protein import in the nucleus is known as a nuclear localization signal. These signals are typically rich in positively charged amino acids such as lysine and proline, forming sequences like -pro-pro-lys-lys-arg-lys-val-. Proteins with a nuclear localization signal are recognized by nuclear transport receptor proteins in the cytosol, facilitating their binding and subsequent entry into the nucleus through nuclear pores. This binding is essential as it leads to the protein complex moving to the nuclear pore where it interacts with nuclear pore fibrils, prompting the pore to open and allowing the nuclear proteins to actively transport into the nucleus, an energy-dependent process using ATP hydrolysis.