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Protein kinase D (PKD/PKCmu) pleckstrin homology (PH) domain Protein Kinase C family is composed of three members, PKD1 (PKCmu), PKD2 and PKD3 (PKCnu). Like the C-type protein kinases (PKCs), PKDs are activated by diacylglycerol (DAG). They are involved in vesicular transport, cell proliferation, survival, migration and immune responses. PKD consists of tandem C1 domains, followed by a PH domain and a kinase domain. While the PKD PH domain has not been shown to bind phosphorylated inositol lipids and is not required for membrane translocation, it is required for nuclear export. 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.",