title: Mms2-Ubc13 covalently bound to ubiquitin reveals the structural basis of linkage-specific polyubiquitin chain formation.
abstract: Lys63-linked polyubiquitin chains participate in nonproteolytic signaling pathways, including regulation of DNA damage tolerance and NF-kappaB activation. E2 enzymes bound to ubiquitin E2 variants (UEV) are vital in these pathways, synthesizing Lys63-linked polyubiquitin chains, but how these complexes achieve specificity for a particular lysine linkage has been unclear. We have determined the crystal structure of an Mms2-Ubc13-ubiquitin (UEV-E2-Ub) covalent intermediate with donor ubiquitin linked to the active site residue of Ubc13. In the structure, the unexpected binding of a donor ubiquitin of one Mms2-Ubc13-Ub complex to the acceptor-binding site of Mms2-Ubc13 in an adjacent complex allows us to visualize at atomic resolution the molecular determinants of acceptor-ubiquitin binding. The structure reveals the key role of Mms2 in allowing selective insertion of Lys63 into the Ubc13 active site and suggests a molecular model for polyubiquitin chain elongation.
authors.affiliation: Department of Biophysics and Biophysical Chemistry and the Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Eddins
authors.forename: Candice M
authors.initials: CM
authors.lastname: Carlile
authors.forename: Kamila M
authors.initials: KM
authors.lastname: Gomez
authors.forename: Cecile M
authors.initials: CM
authors.lastname: Pickart
authors.forename: Cynthia
authors.initials: C
authors.lastname: Wolberger
mesh_terms: D001665:Binding Sites; D008958:Models, Molecular; D025821:Polyubiquitin / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D025801:Ubiquitin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
chemical_list: C112520:MMS2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D025821:Polyubiquitin; C471610:UBC13 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases