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Goodpasture antigen binding protein Pleckstrin homology (PH) domain The GPBP (also called Collagen type IV alpha-3-binding protein/hCERT; START domain-containing protein 11/StARD11; StAR-related lipid transfer protein 11) is a kinase that phosphorylates an N-terminal region of the alpha 3 chain of type IV collagen, which is commonly known as the goodpasture antigen. Its splice variant the ceramide transporter (CERT) mediates the cytosolic transport of ceramide. There have been additional splice variants identified, but all of them function as ceramide transport proteins. GPBP and CERT both contain an N-terminal PH domain, followed by a serine rich domain, and a C-terminal START domain. However, GPBP has an additional serine rich domain just upstream of its START domain. They are members of the oxysterol binding protein (OSBP) family which includes OSBP, OSBP-related proteins (ORP), Goodpasture antigen binding protein (GPBP), and Four phosphate adaptor protein 1 (FAPP1). They have a wide range of purported functions including sterol transport, cell cycle control, pollen development and vessicle transport from Golgi recognize both PI lipids and ARF 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.",