Gated protein transport refers to a highly regulated and selective process by which macromolecules, especially proteins, are transported across the nuclear membrane of eukaryotic cells. This transport occurs through gated channels, known as nuclear pore complexes (NPCs), which are embedded within the nuclear envelope.
The nuclear envelope separates the nucleus from the cytoplasm and consists of two lipid bilayers, known as the inner and outer nuclear membranes, which are connected by NPCs. These NPCs act as gatekeepers, allowing the controlled bidirectional transport of macromolecules between the nucleus and the cytoplasm.
During gated protein transport, proteins destined for the nucleus contain a specific signal sequence, known as a nuclear localization signal (NLS), which allows them to be recognized and selectively transported through the NPCs. Importins, a class of cytoplasmic receptor proteins, bind to the proteins with NLS and facilitate their transport through the NPC. Once inside the nucleus, the protein is released from the importin, which is then recycled back to the cytoplasm.
On the other hand, proteins that need to be transported from the nucleus to the cytoplasm contain a nuclear export signal (NES) sequence. These proteins bind to exportins, which then facilitate their transport through the NPC and into the cytoplasm. Once in the cytoplasm, the protein is dissociated from the exportin, which can be reutilized for further transport.
Gated protein transport plays a crucial role in maintaining cellular homeostasis and allows for precise control of gene expression by regulating the traffic of macromolecules in and out of the nucleus.
