title: Structure of palmitoylated BET3: insights into TRAPP complex assembly and membrane localization.
abstract: BET3 is a component of TRAPP, a complex involved in the tethering of transport vesicles to the cis-Golgi membrane. The crystal structure of human BET3 has been determined to 1.55-A resolution. BET3 adopts an alpha/beta-plait fold and forms dimers in the crystal and in solution, which predetermines the architecture of TRAPP where subunits are present in equimolar stoichiometry. A hydrophobic pocket within BET3 buries a palmitate bound through a thioester linkage to cysteine 68. BET3 and yeast Bet3p are palmitoylated in recombinant yeast cells, the mutant proteins BET3 C68S and Bet3p C80S remain unmodified. Both BET3 and BET3 C68S are found in membrane and cytosolic fractions of these cells; in membrane extractions, they behave like tightly membrane-associated proteins. In a deletion strain, both Bet3p and Bet3p C80S rescue cell viability. Thus, palmitoylation is neither required for viability nor sufficient for membrane association of BET3, which may depend on protein-protein contacts within TRAPP or additional, yet unidentified modifications of BET3. A conformational change may facilitate palmitoyl extrusion from BET3 and allow the fatty acid chain to engage in intermolecular hydrophobic interactions.
authors.affiliation: Max-Delbrück-Centrum für Molekulare Medizin, Berlin, Germany.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Turnbull
authors.forename: Daniel
authors.initials: D
authors.lastname: Kümmel
authors.forename: Bianka
authors.initials: B
authors.lastname: Prinz
authors.forename: Caterina
authors.initials: C
authors.lastname: Holz
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Schultchen
authors.forename: Christine
authors.initials: C
authors.lastname: Lang
authors.forename: Frank H
authors.initials: FH
authors.lastname: Niesen
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Hofmann
authors.forename: Heinrich
authors.initials: H
authors.lastname: Delbrück
authors.forename: Joachim
authors.initials: J
authors.lastname: Behlke
authors.forename: Eva-Christina
authors.initials: EC
authors.lastname: Müller
authors.forename: Ernst
authors.initials: E
authors.lastname: Jarosch
authors.forename: Thomas
authors.initials: T
authors.lastname: Sommer
authors.forename: Udo
authors.initials: U
authors.lastname: Heinemann
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D019281:Dimerization; D006801:Humans; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D019308:Palmitic Acid / Q000737:chemistry; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C098389:BET3 protein, S cerevisiae; D008565:Membrane Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C406327:transport protein particle, TRAPP; D019308:Palmitic Acid