Final answer:
A karyopherin, also known as an importin/exportin, is a carrier protein that aids in the transport of proteins between the cytoplasm and the nucleus. It recognizes specific signals on proteins to guide them through the nuclear pore complex.
Step-by-step explanation:
A karyopherin, also known as an importin/exportin, is a type of carrier protein that facilitates the transport of proteins between the cytoplasm and the nucleus. It plays a vital role in protein transit through a nuclear pore.
When a protein needs to be transported into the nucleus, a karyopherin binds to the protein and acts as a molecular escort, guiding the protein through the nuclear pore complex. The karyopherin recognizes a nuclear localization signal (NLS) on the protein, helping it navigate through the pore.
Similarly, when a protein needs to be exported from the nucleus to the cytoplasm, a different type of karyopherin called an exportin recognizes a nuclear export signal (NES) on the protein and facilitates its transport through the nuclear pore complex.