Domain

Phosphatidylinositol 3-/4-kinase, catalytic domain (IPR000403)

Short name: PI3/4_kinase_cat_dom

Domain relationships

None.

Description

Phosphatidylinositol 3-kinase (PI3-kinase) (EC:2.7.1.137) [PMID: 1322797] is an enzyme that phosphorylates phosphoinositides on the 3-hydroxyl group of the inositol ring. The three products of PI3-kinase - PI-3-P, PI-3,4-P(2) and PI-3,4,5-P(3) function as secondary messengers in cell signalling. Phosphatidylinositol 4-kinase (PI4-kinase) (EC:2.7.1.67) [PMID: 8194527] is an enzyme that acts on phosphatidylinositol (PI) in the first committed step in the production of the secondary messenger inositol-1'4'5'-trisphosphate. This domain is also present in a wide range of protein kinases, involved in diverse cellular functions, such as control of cell growth, regulation of cell cycle progression, a DNA damage checkpoint, recombination, and maintenance of telomere length. Despite significant homology to lipid kinases, no lipid kinase activity has been demonstrated for any of the PIK-related kinases [PMID: 12456783].

The PI3- and PI4-kinases share a well conserved domain at their C-terminal section; this domain seems to be distantly related to the catalytic domain of protein kinases [PMID: 8387896, PMID: 12151228]. The catalytic domain of PI3K has the typical bilobal structure that is seen in other ATP-dependent kinases, with a small N-terminal lobe and a large C-terminal lobe. The core of this domain is the most conserved region of the PI3Ks. The ATP cofactor binds in the crevice formed by the N-and C-terminal lobes, a loop between two strands provides a hydrophobic pocket for binding of the adenine moiety, and a lysine residue interacts with the alpha-phosphate. In contrast to protein kinases, the PI3K loop which interacts with the phosphates of the ATP and is known as the glycine-rich or P-loop, contains no glycine residues. Instead, contact with the ATP -phosphate is maintained through the side chain of a conserved serine residue.

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0016301 kinase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
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Pfam
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