Question

imagine that you have created a protein with an N-terminal ER signal sequence and a C-terminal NLS. Given your understanding of how these signal sequences function, predict what would happen to this protein. Be sure to state the final localization of the protein and provide a brief rationale.

Answer 1

N terminal ER signal sequence :

These signal sequence determine the fate of the protein . ER signal sequence are recognised by the SRP particle present in the cytosol. The SRP particle bind to the Signal sequence of the polypeptide and recruit the polypeptide to the SRP receptor present in the ER membrane. Polypeptide translocate through the translocon present in the ER membrane and enter the ER lumen . Signal sequence are cleaved by the signal peptidase enzyme present in the ER lumen. Chaperone bind to the polypeptide and result in proper folding of the protein.

C terminal NLS sequence:

Protein containing nuclear localisation signal are recognised by the importin receptor which escort the protein from the cytoplasm to the nucleus through nuclear pore complex.