Pleckstrin homology domain-containing family O Pleckstrin homology domain
The PLEKHO family members are PLEKHO1 (also called CKIP-1/Casein kinase 2-interacting protein 1/CK2-interacting protein 1) and PLEKHO2 (PLEKHQ1/PH domain-containing family Q member 1). They both contain a single PH domain. PLEKHO1 acts as a scaffold protein that functions in plasma membrane recruitment, transcriptional activity modulation, and posttranscriptional modification regulation. As an adaptor protein it is involved in signaling pathways, apoptosis, differentiation, cytoskeleton, and bone formation. Not much is know about PLEKHO2. 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.",