Protein S (also referred to as PROS) is a vitamin Ok-dependent plasma glycoprotein synthesized within the liver. Within the circulation, Protein S exists in two types: a free type and a posh type sure to enrich protein C4b-binding protein (C4BP). In people, protein S is encoded by the PROS1 gene.[5][6]
Contents
Historical past[edit]
Protein S is called for Seattle, Washington, the place it was initially found and purified[7] by Earl Davie’s group in 1977.[8]
Construction[edit]
Protein S is partly homologous to different vitamin Ok-dependent plasma coagulation proteins, similar to protein C and components VII, IX, and X. Just like them, it has a Gla area and several other EGF-like domains (4 reasonably than two), however no serine protease area. As a substitute, there’s a giant C-terminus area that’s homologous to plasma steroid hormone-binding proteins similar to intercourse hormone-binding globulin and corticosteroid-binding globulin. It might play a task within the protein capabilities as both a cofactor for activated protein C (APC) or in binding C4BP.[9][10]
Moreover, protein S has a peptide between the Gla area and the EGF-like area, that’s cleaved by thrombin. The Gla and EGF-like domains keep related after the cleavage by a disulfide bond. Nonetheless, protein S loses its operate as an APC cofactor following both this cleavage or binding C4BP.[11]
Operate[edit]
The very best characterised operate of Protein S is its position within the anti coagulation pathway, the place it capabilities as a cofactor to Protein C within the inactivation of Components Va and VIIIa. Solely the free type has cofactor exercise.[12]
Protein S binds to negatively charged phospholipids through the carboxylated Gla area. This property permits Protein S to facilitate the removing of cells which can be present process apoptosis, a type of structured cell loss of life utilized by the physique to take away undesirable or broken cells. In wholesome cells, an ATP (adenosine triphosphate)-dependent enzyme removes negatively charged phospholipids similar to phosphatidyl serine from the outer leaflet of the cell membrane. An apoptotic cell (that’s, one present process apoptosis) now not actively manages the distribution of phospholipids in its outer membrane and therefore begins to show negatively charged phospholipids on its exterior floor. These negatively charged phospholipids are acknowledged by phagocytes similar to macrophages. Protein S binds to the negatively charged phospholipids and capabilities as a bridge between the apoptotic cell and the phagocyte. This bridging expedites phagocytosis and permits the cell to be eliminated with out giving rise to irritation or different indicators of tissue injury.
Protein S additionally binds to the nascent complement complicated C5,6,7 and prevents this complicated from inserting right into a membrane. This operate prevents the inappropriate activation of the complement system, which might trigger uncontrolled systemic irritation. In truth, Protein S was first found in 1977 on this position and it’s named after the membrane website that it occupies within the complicated.[13]
Pathology[edit] – “s protein”
Mutations within the PROS1 gene can result in Protein S deficiency which is a uncommon blood dysfunction which may result in an elevated danger of thrombosis.[14][15]
Interactions[edit]
Protein S has been proven to work together with Issue V.[16][17]
See additionally[edit]
“s protein”