Tyrosine-protein kinase JAK3 is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that in humans is encoded by the JAK3 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.
Since JAK3 expression is restricted mostly to hematopoietic cells, its role in cytokine signaling is thought to be more restricted than other JAKs. It is most commonly expressed in T cells and NK cells, but has been induced in other leukocytes, including monocytes. Jak3 is involved in signal transduction by receptors that employ the common gamma chain

Common gamma chain

The common gamma chain , also known as interleukin-2 receptor subunit gamma or IL-2RG, is a cytokine receptor sub-unit that is common to the receptor complexes for at least six different interleukin receptors: IL-2, IL-4, IL-7, IL-9, IL-15 and interleukin-21 receptor...

 (γC) of the type I cytokine receptor

Type I cytokine receptor

Type I cytokine receptors are transmembrane receptors expressed on the surface of cells that recognize and respond to cytokines with four α-helical strands. These receptors are also known under the name hemopoietin receptors, and share a common amino acid motif in the extracellular portion...

 family (e.g. IL-2R, IL-4R, IL-7R, IL-9R, IL-15R, and IL-21R).
Mutations of JAK3 result in severe combined immunodeficiency (SCID). Mice that do not express JAK3 have T-cells and B-cells that fail to respond to many cytokines.

Interactions

Janus kinase 3 has been shown to interact

Protein-protein interaction

Protein–protein interactions occur when two or more proteins bind together, often to carry out their biological function. Many of the most important molecular processes in the cell such as DNA replication are carried out by large molecular machines that are built from a large number of protein...

 with CD247

CD247

T-cell surface glycoprotein CD3 zeta chain also known as T-cell receptor T3 zeta chain or CD247 is a protein that in humans is encoded by the CD247 gene.- Genomics :...

, TIAF1

TIAF1

TGFB1-induced anti-apoptotic factor 1 is a protein that in humans is encoded by the TIAF1 gene.-Interactions:TIAF1 has been shown to interact with Janus kinase 3 and TRIB3.-Further reading:...

 and IL2RG.

Further reading

External links