title: Molecular basis for recognition of dilysine trafficking motifs by COPI.
abstract: COPI mediates retrograde trafficking from the Golgi to the endoplasmic reticulum (ER) and within the Golgi stack, sorting transmembrane proteins bearing C-terminal KKxx or KxKxx motifs. The structure of KxKxx motifs bound to the N-terminal WD-repeat domain of β'-COP identifies electrostatic contacts between the motif and complementary patches at the center of the β'-COP propeller. An absolute requirement of a two-residue spacing between the terminal carboxylate group and first lysine residue results from interactions of carbonyl groups in the motif backbone with basic side chains of β'-COP. Similar interactions are proposed to mediate binding of KKxx motifs by the homologous α-COP domain. Mutation of key interacting residues in either domain or in their cognate motifs abolishes in vitro binding and results in mistrafficking of dilysine-containing cargo in yeast without compromising cell viability. Flexibility between β'-COP WD-repeat domains and the location of cargo binding have implications for COPI coat assembly.
authors.affiliation: Cambridge Institute for Medical Research, Department of Clinical Biochemistry, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK. lpj21@cam.ac.uk
authors.forename: Lauren P
authors.initials: LP
authors.lastname: Jackson
authors.forename: Michael
authors.initials: M
authors.lastname: Lewis
authors.forename: Helen M
authors.initials: HM
authors.lastname: Kent
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Edeling
authors.forename: Philip R
authors.initials: PR
authors.lastname: Evans
authors.forename: Rainer
authors.initials: R
authors.lastname: Duden
authors.forename: David J
authors.initials: DJ
authors.lastname: Owen
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D020755:Coat Protein Complex I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020756:Coatomer Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004151:Dipeptides / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000138:chemical synthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D020755:Coat Protein Complex I; D020756:Coatomer Protein; D004151:Dipeptides; D029701:Saccharomyces cerevisiae Proteins; C024575:lysyllysine