Final answer:
In the context of nuclear transport of proteins, the correct true or false sequence for the statements provided is TFTT. Key components involve nuclear transport receptors, adaptor proteins, and the GTPase Ran, which all play critical roles in the import and export of proteins through the nuclear pore complex.
Step-by-step explanation:
The process of nuclear transport of proteins is complex and involves a variety of molecular interactions. Proteins that need to enter the nucleus are typically recognized by their nuclear localization signals (NLS), which are rich in positively charged amino acids. These signals facilitate the binding of proteins to nuclear transport receptors, also known as importins, which then guide the proteins through the nuclear pore complex (NPC) into the nucleus. Conversely, nuclear export signals (NES) on proteins destined for the cytoplasm bind to exportins, which mediate their passage out of the nucleus.
- Statement 1 (T): Many nuclear import and export receptors are indeed members of the same protein family. They share similar structural domains that allow them to interact with the nuclear pore complex and the cargo proteins.
- Statement 2 (F): It is incorrect to state that most nuclear import receptors contain unstructured domains with FG-repeats; rather, it is the nuclear pore complex itself that contains proteins with FG-repeats that interact with the nuclear transport receptors.
- Statement 3 (T): Certain nuclear cargo proteins do indeed require adaptor proteins to facilitate their import into the nucleus by simultaneously binding to nuclear localization signals and importins.
- Statement 4 (T): Ran, a small GTPase, is predominantly found in its GTP-bound form in the nucleus, which is crucial for the directionality of nuclear transport.
The correct sequence of True or False statements is therefore: T, F, T, T.