University:
Swansea University
Course:
PM-133 | Evolutionary and Molecular Genetics
Academic year:

2023
Views:

449

Pages:

2
Author:

Amal J.

Protein Trafficking Overview: Protein trafficking refers to the process by which proteins are transported to their specific destinations within or outside the cell. This process involves a series of steps guided by signal sequences within the amino acids of the proteins. Pathways: Secretory Pathway: Involves proteins destined for secretion outside the cell, plasma membrane, lysosomes, and other organelles like the Golgi apparatus. Process: Proteins enter the Endoplasmic Reticulum (ER) for modification (such as disulfide bond formation and glycosylation). They are packaged into vesicles, transported to the Golgi, and finally directed to their destination. The default fate for these proteins is to be secreted out of the cell. Cytosolic Pathway: Proteins that do not enter the ER follow the cytosolic pathway. These proteins are typically directed to mitochondria, chloroplasts, the nucleus, peroxisomes, or remain in the cytosol. Destinations: Mitochondria Chloroplasts Nucleus Peroxisomes Cytosol Signal Sequences: Proteins contain specific amino acid sequences that act as signals, directing them to their appropriate cellular locations. N-terminal Signal Sequence: A key determinant for entry into the ER, rich in positively charged and hydrophobic residues. Directs the protein to the ER, where it undergoes further processing. Signal Recognition Particle (SRP): SRP binds to the N-terminal signal sequence and directs the ribosome to the ER membrane, where protein synthesis continues. ER (Endoplasmic Reticulum): The ER plays a crucial role in protein synthesis, especially for proteins destined for secretion or membrane localization. Rough ER: Studded with ribosomes, is the site of protein synthesis. Smooth ER: Involved in lipid synthesis and detoxification. Protein Modification and Transport: Once synthesized, proteins undergo modifications such as glycosylation and disulfide bond formation in the ER and Golgi apparatus. They are then packaged into vesicles and transported to their specific destinations, such as the plasma membrane, lysosomes, or secreted outside the cell.