What is the Sec pathway?
The general secretory (Sec) pathway comprises an essential, ubiquitous and universal export machinery for most proteins that integrate into, or translocate through, the plasma membrane. Sec exportome polypeptides are synthesized as pre-proteins that have cleavable signal peptides fused to the exported mature domains.
How does the SEC pathway work?
In bacteria, two major pathways exist to secrete proteins across the cytoplasmic membrane. The general Secretion route, termed Sec-pathway, catalyzes the transmembrane translocation of proteins in their unfolded conformation, whereupon they fold into their native structure at the trans-side of the membrane.
How do proteins leave the cell membrane?
Proteins can be secreted from cells by exocytosis in either a constitutive or a regulated fashion. In the regulated pathways, molecules are stored either in secretory vesicles or synaptic vesicles, which do not fuse with the plasma membrane to release their contents until an appropriate signal is received.
What are the steps of the protein pathway?
It includes three steps: initiation, elongation, and termination. After the mRNA is processed, it carries the instructions to a ribosome in the cytoplasm. Translation occurs at the ribosome, which consists of rRNA and proteins.
What is SEC protein?
Size-exclusion chromatography (SEC), also known as gel filtration, separates proteins based on their sizes (hydrodynamic radii versus absolute molecular weight) in solution with larger sized species eluting before smaller proteins.
What is SEC dependent pathway?
A combination of bacterial genetics, development of an in vitro membrane vesicle system and the concurrent elaboration of the signal hypothesis from studies on eukaryotes led to the identification and characterization of two pathways leading to protein export through the SecYEG cytoplasmic membrane translocon.
How do proteins get to their correct destinations in cells?
Transport through the endomembrane system In the ER, proteins fold into their correct shapes, and may also get sugar groups attached to them. Most proteins are then transported to the Golgi apparatus in membrane vesicles. These destinations include lysosomes, the plasma membrane, and the cell exterior.
How are proteins transported out of the endoplasmic reticulum to the Golgi apparatus?
Correctly folded and assembled proteins in the ER are packaged into COPII-coated transport vesicles that pinch off from the ER membrane. Shortly thereafter the coat is shed and the vesicles fuse with one another to form vesicular tubular clusters, which move on microtubule tracks to the Golgi apparatus.
What is the principle of SEC?
The underlying principle of SEC is that particles of different sizes elute (filter) through a stationary phase at different rates. This results in the separation of a solution of particles based on size.
How are proteins exported through the Sec pathway?
The general secretory (Sec) pathway comprises an essential, ubiquitous and universal export machinery for most proteins that integrate into, or translocate through, the plasma membrane. Sec exportome polypeptides are synthesized as pre-proteins that have cleavable signal peptides fused to the exported mature domains.
Where does the secretion of unfolded proteins take place?
The general secretion (Sec) involves secretion of unfolded proteins that first remain inside the cells. In Gram-negative bacteria, the secreted protein is sent to either the inner membrane or the periplasm.
Which is a nonclassical pathway for protein secretion?
At least four nonclassical (unconventional) protein secretion pathways have been described. They include 1) direct translocation of proteins across the plasma membrane likely through membrane transporters, 2) blebbing, 3) lysosomal secretion, and 4) release via exosomes derived from multivesicular bodies.
Where does the secretory pathway take place in the cell?
The secretory pathway refers to the endoplasmic reticulum, Golgi apparatus and the vesicles that travel in between them as well as the cell membrane and lysosomes. It’s named ‘secretory’ for being the pathway by which the cell secretes proteins into the extracellular environment.