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Reviewed October 2009
What is the official name of the PROS1 gene?
The official name of this gene is “protein S (alpha).”
PROS1 is the gene's official symbol. The PROS1 gene is also known by other names, listed below.
Read more about gene names and symbols on the About page.
What is the normal function of the PROS1 gene?
The PROS1 gene provides instructions for making a protein called protein S that is important for controlling blood clotting. By itself, protein S cannot carry out the chemical reactions necessary for regulating the formation of blood clots. Instead, protein S attaches to certain enzymes and enhances their function. On the basis of this action, protein S is called a cofactor.
Protein S is made chiefly by cells in the liver. The protein circulates in the bloodstream in two forms; it is either attached (bound) to a specific protein or occurs by itself in a free form. Both forms of proteins S can act as cofactors; however, bound protein S is less effective than the free form. Protein S is a cofactor for an enzyme called activated protein C (APC). APC turns off (inactivates) the blood clotting proteins known as factor Va and factor VIIIa. Protein S also helps an enzyme known as tissue factor pathway inhibitor (TFPI) block the activity of another clotting protein, factor Xa.
How are changes in the PROS1 gene related to health conditions?
Where is the PROS1 gene located?
Cytogenetic Location: 3q11.2
Molecular Location on chromosome 3: base pairs 93,873,037 to 93,974,090
(Homo sapiens Annotation Release 107, GRCh38.p2) (
The PROS1 gene is located on the long (q) arm of chromosome 3 at position 11.2.
More precisely, the PROS1 gene is located from base pair 93,873,037 to base pair 93,974,090 on chromosome 3.
See How do geneticists indicate the location of a gene? in the Handbook.
Where can I find additional information about PROS1?
You and your healthcare professional may find the following resources about PROS1 helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
What other names do people use for the PROS1 gene or gene products?
See How are genetic conditions and genes named? in the Handbook.
Where can I find general information about genes?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding PROS1?
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (8 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.