6mw8 | pdb_00006mw8
UDP-galactose:glucoside-Skp1 alpha-D-galactosyltransferase with bound UDP and Manganese
Structural highlights
Publication Abstract from PubMedSkp1, a subunit of E3 Skp1/Cullin-1/F-box protein ubiquitin ligases, is modified by a prolyl hydroxylase that mediates O2 regulation of the social amoeba Dictyostelium and the parasite Toxoplasma gondii The full effect of hydroxylation requires modification of the hydroxyproline by a pentasaccharide that, in Dictyostelium, influences Skp1 structure to favor assembly of Skp1/F-box protein subcomplexes. In Toxoplasma, the presence of a contrasting penultimate sugar assembled by a different glycosyltransferase enables testing of the conformational control model. To define the final sugar and its linkage, here we identified the glycosyltransferase that completes the glycan and found that it is closely related to glycogenin, an enzyme that may prime glycogen synthesis in yeast and animals. However, the Toxoplasma enzyme catalyzes formation of a Galalpha1,3Glcalpha linkage rather than the Glcalpha1,4Glcalpha linkage formed by glycogenin. Kinetic and crystallographic experiments showed that the glycosyltransferase Gat1 is specific for Skp1 in Toxoplasma and also in another protist, the crop pathogen Pythium ultimum The fifth sugar is important for glycan function as indicated by the slow-growth phenotype of gat1Delta parasites. Computational analyses indicated that, despite the sequence difference, the Toxoplasma glycan still assumes an ordered conformation that controls Skp1 structure and revealed the importance of nonpolar packing interactions of the fifth sugar. The substitution of glycosyltransferases in Toxoplasma and Pythium by an unrelated bifunctional enzyme that assembles a distinct but structurally compatible glycan in Dictyostelium is a remarkable case of convergent evolution, which emphasizes the importance of the terminal alpha-galactose and establishes the phylogenetic breadth of Skp1 glycoregulation. A terminal alpha3-galactose modification regulates an E3 ubiquitin ligase subunit in Toxoplasma gondii.,Mandalasi M, Kim HW, Thieker D, Sheikh MO, Gas-Pascual E, Rahman K, Zhao P, Daniel NG, van der Wel H, Ichikawa HT, Glushka JN, Wells L, Woods RJ, Wood ZA, West CM J Biol Chem. 2020 Jul 3;295(27):9223-9243. doi: 10.1074/jbc.RA120.013792. Epub, 2020 May 15. PMID:32414843[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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