Autophagy-related protein 26/Sterol 3-beta-glucosyltransferase Pleckstrin homology (PH) domain, repeat 2
ATG26 (also called UGT51/UDP-glycosyltransferase 51), a member of the glycosyltransferase 28 family, resulting in the biosynthesis of sterol glucoside. ATG26 in decane metabolism and autophagy. There are 32 known autophagy-related (ATG) proteins, 17 are components of the core autophagic machinery essential for all autophagy-related pathways and 15 are the additional components required only for certain pathways or species. The core autophagic machinery includes 1) the ATG9 cycling system (ATG1, ATG2, ATG9, ATG13, ATG18, and ATG27), 2) the phosphatidylinositol 3-kinase complex (ATG6/VPS30, ATG14, VPS15, and ATG34), and 3) the ubiquitin-like protein system (ATG3, ATG4, ATG5, ATG7, ATG8, ATG10, ATG12, and ATG16). Less is known about how the core machinery is adapted or modulated with additional components to accommodate the nonselective sequestration of bulk cytosol (autophagosome formation) or selective sequestration of specific cargos (Cvt vesicle, pexophagosome, or bacteria-containing autophagosome formation). The pexophagosome-specific additions include the ATG30-ATG11-ATG17 receptor-adaptors complex, the coiled-coil protein ATG25, and the sterol glucosyltransferase ATG26. ATG26 is necessary for the degradation of medium peroxisomes. It contains 2 GRAM domains and a single PH domain. PH domains are only found in eukaryotes. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. PH domains also have diverse functions. They are often involved in targeting proteins to the plasma membrane, but 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.
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