title: Structure of a compact conformation of linear diubiquitin.
abstract: Post-translational modifications involving ubiquitin regulate a wide range of biological processes including protein degradation, responses to DNA damage and immune signalling. Ubiquitin polymerizes into chains which may contain eight different linkage types; the ubiquitin C-terminal glycine can link to one of the seven lysine residues or the N-terminal amino group of methionine in the distal ubiquitin molecule. The latter head-to-tail linkage type, referred to as a linear ubiquitin chain, is involved in NF-κB activation through specific interactions with NF-κB essential modulator (NEMO). Here, a crystal structure of linear diubiquitin at a resolution of 2.2 Å is reported. Although the two ubiquitin moieties do not interact with each other directly, the overall structure adopts a compact but not completely closed conformation with a few intermoiety contacts. This structure differs from the previously reported extended conformation, which resembles Lys63-linked diubiquitin, suggesting that the linear polyubiquitin chain is intrinsically flexible and can adopt multiple conformations.
authors.affiliation: Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Rohaim
authors.forename: Masato
authors.initials: M
authors.lastname: Kawasaki
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Kato
authors.forename: Ivan
authors.initials: I
authors.lastname: Dikic
authors.forename: Soichi
authors.initials: S
authors.lastname: Wakatsuki
mesh_terms: D018360:Crystallography, X-Ray; D006801:Humans; D008239:Lysine / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D016328:NF-kappa B / Q000378:metabolism; D011487:Protein Conformation; D014452:Ubiquitins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D016328:NF-kappa B; C109184:UBD protein, human; D014452:Ubiquitins; D008239:Lysine