A secretory protein is any protein, whether it be endocrine or exocrine, which is secreted by a cell. Secretory proteins include many hormones, enzymes, toxins, and antimicrobial peptides. Secretory proteins are synthesized in the endoplasmic reticulum.[1]
The production of a secretory protein starts like any other protein. The mRNA is produced and transported to the cytosol where it interacts with a free cytosolic ribosome. The part that is produced first, the N-terminal, contains a signal sequence consisting of 6 to 12 amino acids with hydrophobic side chains. This sequence is recognised by a cytosolic protein, SRP (Signal Recognition Particle), which stops the translation and aids in the transport of the mRNA-ribosome complex to an SRP receptor found in the membrane of the endoplasmic reticulum. When it arrives at the ER, the signal sequence is transferred to the translocon, a protein-conducting channel in the membrane that allows the newly synthesized polypeptide to be translocated to the ER lumen. The dissociation of SRP from the ribosome restores the translation of the secretory protein. The signal sequence is removed and the translation continues while the produced chain moves through the translocon (cotranslational translocation).
Modificationedit
After the production of the protein is completed, it interacts with several other proteins to gain its final state.
Endoplasmic reticulumedit
After translation, proteins within the ER make sure that the protein is folded correctly. If after a first attempt the folding is unsuccessful, a second folding is attempted. If this fails too the protein is exported to the cytosol and labelled for destruction. Aside from the folding, there is also a sugar chain added to the protein. After these changes, the protein is transported to the Golgi apparatus by a coated vesicle using coating protein COPII.
Golgi apparatusedit
In the Golgi apparatus, the sugar chains are modified by adding or removing certain sugars. The secretory protein leaves the Golgi apparatus by an uncoated vesicle.
Secretionedit
Membrane proteins with functional areas on the cytosolic side of both the vesicle and cell membrane make sure the vesicle associates with the membrane. The vesicle membrane fuses with the cell membrane and so the protein leaves the cell. Some vesicles don't fuse immediately and await a signal before starting the fusing. This is seen in vesicles carrying neurotransmitter in presynaptic cells. This process constitutes an effective cell-cell signaling mechanism via membrane vesicle trafficking from secretory cell to the target cells in human or animal body. Recently, the process has been extended to the host–pathogen interface, wherein, gram negative microbes secrete bacterial outer membrane vesicles containing fully conformed signal proteins and virulence factors via exocytosis of nano-sized vesicles, in order to control host or target cell activities and exploit their environment.
UniProt contains manually curated secretory proteins. There are also computationally predicted secretory protein databases, these databases are listed in the secretome section.
^Lodish H, Berk A, Zipursky SL, Matsudaira P, Baltimore D, Darnell J (2000). "Chapter 17.3: Overview of the Secretory Pathway". Molecular Cell Biology (4th ed.). W. H. Freeman. ISBN978-0-7167-3706-3.
External linksedit
"Localization: Secreted". Orientations of Proteins in Membranes (OPM) database.
April 14, 2024
secretory, protein, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, january. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Secretory protein news newspapers books scholar JSTOR January 2021 Learn how and when to remove this template message A secretory protein is any protein whether it be endocrine or exocrine which is secreted by a cell Secretory proteins include many hormones enzymes toxins and antimicrobial peptides Secretory proteins are synthesized in the endoplasmic reticulum 1 Contents 1 Production 2 Modification 2 1 Endoplasmic reticulum 2 2 Golgi apparatus 3 Secretion 4 Sequence data and related databases 5 See also 6 References 7 External linksProduction editThe production of a secretory protein starts like any other protein The mRNA is produced and transported to the cytosol where it interacts with a free cytosolic ribosome The part that is produced first the N terminal contains a signal sequence consisting of 6 to 12 amino acids with hydrophobic side chains This sequence is recognised by a cytosolic protein SRP Signal Recognition Particle which stops the translation and aids in the transport of the mRNA ribosome complex to an SRP receptor found in the membrane of the endoplasmic reticulum When it arrives at the ER the signal sequence is transferred to the translocon a protein conducting channel in the membrane that allows the newly synthesized polypeptide to be translocated to the ER lumen The dissociation of SRP from the ribosome restores the translation of the secretory protein The signal sequence is removed and the translation continues while the produced chain moves through the translocon cotranslational translocation Modification editAfter the production of the protein is completed it interacts with several other proteins to gain its final state Endoplasmic reticulum edit After translation proteins within the ER make sure that the protein is folded correctly If after a first attempt the folding is unsuccessful a second folding is attempted If this fails too the protein is exported to the cytosol and labelled for destruction Aside from the folding there is also a sugar chain added to the protein After these changes the protein is transported to the Golgi apparatus by a coated vesicle using coating protein COPII Golgi apparatus edit In the Golgi apparatus the sugar chains are modified by adding or removing certain sugars The secretory protein leaves the Golgi apparatus by an uncoated vesicle Secretion editMembrane proteins with functional areas on the cytosolic side of both the vesicle and cell membrane make sure the vesicle associates with the membrane The vesicle membrane fuses with the cell membrane and so the protein leaves the cell Some vesicles don t fuse immediately and await a signal before starting the fusing This is seen in vesicles carrying neurotransmitter in presynaptic cells This process constitutes an effective cell cell signaling mechanism via membrane vesicle trafficking from secretory cell to the target cells in human or animal body Recently the process has been extended to the host pathogen interface wherein gram negative microbes secrete bacterial outer membrane vesicles containing fully conformed signal proteins and virulence factors via exocytosis of nano sized vesicles in order to control host or target cell activities and exploit their environment Sequence data and related databases editEffective database 2010 UniProt contains manually curated secretory proteins There are also computationally predicted secretory protein databases these databases are listed in the secretome section See also editBacterial outer membrane vesicles Exocytosis Host pathogen interaction Membrane vesicle trafficking Secretion Secretome SecretomicsReferences edit Lodish H Berk A Zipursky SL Matsudaira P Baltimore D Darnell J 2000 Chapter 17 3 Overview of the Secretory Pathway Molecular Cell Biology 4th ed W H Freeman ISBN 978 0 7167 3706 3 External links edit Localization Secreted Orientations of Proteins in Membranes OPM database Retrieved from https en wikipedia org w index php title Secretory protein amp oldid 1186552075, wikipedia, wiki, book, books, library,
