4gu2

Crystal structure of ubiquitin from Entamoeba histolytica to 1.35 Angstrom

spinqualitylabelsall models 4gu2, resolution 1.35Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4gu2 is a 1 chain structure with sequence from Entamoeba histolytica. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function C4M760_ENTHI Publication Abstract from PubMed Ubiquitination is important for numerous cellular processes in most eukaryotic organisms, including cellular proliferation, development, and protein turnover by the proteasome. The intestinal parasite Entamoeba histolytica harbors an extensive ubiquitin-proteasome system. Proteasome inhibitors are known to impair parasite proliferation and encystation, suggesting the ubiquitin-proteasome pathway as a viable therapeutic target. However, no functional studies of the E. histolytica ubiquitination enzymes have yet emerged. Here, we have cloned and characterized multiple E. histolytica ubiquitination components, spanning ubiquitin and its activating (E1), conjugating (E2), and ligating (E3) enzymes. Crystal structures of EhUbiquitin reveal a clustering of unique residues on the alpha1 helix surface, including an eighth surface lysine not found in other organisms, that may allow for a unique polyubiquitin linkage in E. histolytica. EhUbiquitin is activated by and forms a thioester bond with EhUba1 (E1) in vitro, in an ATP- and magnesium-dependent fashion. EhUba1 exhibits a greater maximal initial velocity of pyrophosphate:ATP exchange than its human homolog, suggesting different kinetics of ubiquitin activation in E. histolytica. EhUba1 engages the E2 enzyme EhUbc5 through its ubiquitin-fold domain to transfer the EhUbiquitin thioester. However, EhUbc5 has a >10-fold preference for EhUba1~Ub compared to unconjugated EhUba1. A crystal structure of EhUbc5 allowed prediction of a non-covalent backside interaction with EhUbiquitin and with E3 enzymes. EhUbc5 selectively engages EhRING1 (E3) to the exclusion of two HECT family E3 ligases, and mutagenesis indicates a conserved mode of E2/RING-E3 interaction in E. histolytica. Structural determinants of ubiquitin conjugation in Entamoeba histolytica.,Bosch DE, Siderovski DP J Biol Chem. 2012 Dec 3. PMID:23209297 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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