title: Cyclisation of Lys48-linked diubiquitin in vitro and in vivo.
abstract: Ubiquitin (Ub) is able to form polymeric isopeptide-linked chains through condensation of any of its seven lysine (Lys) residues with the C-terminus of an adjacent Ub monomer. Electrospray ionisation mass spectrometry (ESI-MS) of commercial in vitro-generated Lys48-linked di-Ub (Lys48-Ub(2)) revealed a major population of cyclised dimer. The absence of a free C-terminus in this population was confirmed by an inability to bind the zinc finger ubiquitin-binding domain (ZnF-UBP) of USP5/isopeptidase-T. Endogenous Ub(2) purified from skeletal muscle and cultured mammalian cells was found to contain cyclic Lys48-Ub(2), demonstrating that cyclisation of poly-Ub can also occur in vivo.
authors.affiliation: School of Chemistry, University of Nottingham, Nottingham, UK.
authors.forename: Kleitos
authors.initials: K
authors.lastname: Sokratous
authors.forename: Joanna
authors.initials: J
authors.lastname: Strachan
authors.forename: Lucy V
authors.initials: LV
authors.lastname: Roach
authors.forename: Robert
authors.initials: R
authors.lastname: Layfield
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Oldham
mesh_terms: D000818:Animals; D002846:Chromatography, Affinity; D006801:Humans; D018482:Muscle, Skeletal / Q000378:metabolism; D051381:Rats; D021241:Spectrometry, Mass, Electrospray Ionization; D014452:Ubiquitins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D014452:Ubiquitins