Tandem PH-domain-containing protein 2 Pleckstrin homology (PH) domain
The binding of TAPP2 (also called PLEKHA2) adaptors to PtdIns(3,4)P(2), but not PI(3,4, 5)P3, function as negative regulators of insulin and PI3K signalling pathways (i.e. TAPP/utrophin/syntrophin complex). TAPP2 contains two sequential PH domains in which the C-terminal PH domain specifically binds PtdIns(3,4)P2 with high affinity. The N-terminal PH domain does not interact with any phosphoinositide tested. They also contain a C-terminal PDZ-binding motif that interacts with several PDZ-binding proteins, including PTPN13 (known previously as PTPL1 or FAP-1) as well as the scaffolding proteins MUPP1 (multiple PDZ-domain-containing protein 1), syntrophin and utrophin. The members here are most sequence similar to TAPP2 proteins, but may not be actual TAPP2 proteins. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.
Jiyao W et al.(2023). "The conserved domain database in 2023.",