5ux6
Structure of Human POFUT1 in its apo form
Structural highlights
DiseaseOFUT1_HUMAN Dowling-Degos disease. The disease is caused by mutations affecting the gene represented in this entry. FunctionOFUT1_HUMAN Catalyzes the reaction that attaches fucose through an O-glycosidic linkage to a conserved serine or threonine residue found in the consensus sequence C2-X(4,5)-[S/T]-C3 of EGF domains, where C2 and C3 are the second and third conserved cysteines. Specifically uses GDP-fucose as donor substrate and proper disulfide pairing of the substrate EGF domains is required for fucose transfer. Plays a crucial role in NOTCH signaling. Initial fucosylation of NOTCH by POFUT1 generates a substrate for FRINGE/RFNG, an acetylglucosaminyltransferase that can then extend the fucosylation on the NOTCH EGF repeats. This extended fucosylation is required for optimal ligand binding and canonical NOTCH signaling induced by DLL1 or JAGGED1. Fucosylates AGRN and determines its ability to cluster acetylcholine receptors (AChRs).[1] [2] Publication Abstract from PubMedProtein O-fucosyltransferase-1 (POFUT1), which transfers fucose residues to acceptor sites on serine and threonine residues of epidermal growth factor-like repeats of recipient proteins, is essential for Notch signal transduction in mammals. Here, we examine the consequences of POFUT1 loss on the oncogenic signaling associated with certain leukemia-associated mutations of human Notch1, report the structures of human POFUT1 in free and GDP-fucose bound states, and assess the effects of Dowling-Degos mutations on human POFUT1 function. CRISPR-mediated knockout of POFUT1 in U2OS cells suppresses both normal Notch1 signaling, and the ligand-independent signaling associated with leukemogenic mutations of Notch1. Normal and oncogenic signaling are rescued by wild-type POFUT1 but rescue is impaired by an active-site R240A mutation. The overall structure of the human enzyme closely resembles that of the Caenorhabditis elegans protein, with an overall backbone RMSD of 0.93 A, despite primary sequence identity of only 39% in the mature protein. GDP-fucose binding to the human enzyme induces limited backbone conformational movement, though the side chains of R43 and D244 reorient to make direct contact with the fucose moiety in the complex. The reported Dowling-Degos mutations of POFUT1, except for M262T, fail to rescue Notch1 signaling efficiently in the CRISPR-engineered POFUT1-/- background. Together, these studies identify POFUT1 as a potential target for cancers driven by Notch1 mutations and provide a structural roadmap for its inhibition. Structure of human POFUT1, its requirement in ligand-independent oncogenic Notch signaling, and functional effects of Dowling-Degos mutations.,McMillan BJ, Zimmerman B, Egan ED, Lofgren M, Xu X, Hesser A, Blacklow SC Glycobiology. 2017 Mar 17:1-10. doi: 10.1093/glycob/cwx020. PMID:28334865[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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