Phosphatase Subfamily PPIP5K

Phosphatase Classification: Fold HP: Superfamily HP (histidine phosphatase): Family HP, branch 2: PPIP5K

PPIP5K is a phosphoinositol kinase that also has a pseudophosphatase domain which bind to PtdIns(3,4,5)P3. PPIP5K converts InsP6 and 5-InsP7 to 1-InsP7 and InsP8.

Evolution

PPIP5K is found in most eukaryotes. Most vertebrates have at least two copies, while invertebrates usually have one.

Domain

PPIP5K has two domains: N-terminal RimK/ATP-grasp domain, and C-terminal HP2 domain [1]. The RimK is the active kinase domain [1, 2].

Unlike other members of HP2 family which are protein or non-protein phosphatases, the HP2 domain of PPIP5K is not catalytically active. Instead, this HP2 domain is specialized for binding PtdIns(3,4,5)P3, as a partial PH (pleckstrin homology) consensus sequence is spliced into this HP2 domain [3].

References

1. Fridy PC, Otto JC, Dollins DE, and York JD. Cloning and characterization of two human VIP1-like inositol hexakisphosphate and diphosphoinositol pentakisphosphate kinases. J Biol Chem. 2007 Oct 19;282(42):30754-62. DOI:10.1074/jbc.M704656200 |
2. Choi JH, Williams J, Cho J, Falck JR, and Shears SB. Purification, sequencing, and molecular identification of a mammalian PP-InsP5 kinase that is activated when cells are exposed to hyperosmotic stress. J Biol Chem. 2007 Oct 19;282(42):30763-75. DOI:10.1074/jbc.M704655200 |
3. Gokhale NA, Zaremba A, and Shears SB. Receptor-dependent compartmentalization of PPIP5K1, a kinase with a cryptic polyphosphoinositide binding domain. Biochem J. 2011 Mar 15;434(3):415-26. DOI:10.1042/BJ20101437 |