title: The complex interactions of Chs5p, the ChAPs, and the cargo Chs3p.
abstract: The exomer complex is a putative vesicle coat required for the direct transport of a subset of cargoes from the trans-Golgi network (TGN) to the plasma membrane. Exomer comprises Chs5p and the ChAPs family of proteins (Chs6p, Bud7p, Bch1p, and Bch2p), which are believed to act as cargo receptors. In particular, Chs6p is required for the transport of the chitin synthase Chs3p to the bud neck. However, how the ChAPs associate with Chs5p and recognize cargo is not well understood. Using domain-switch chimeras of Chs6p and Bch2p, we show that four tetratricopeptide repeats (TPRs) are involved in interaction with Chs5p. Because these roles are conserved among the ChAPs, the TPRs are interchangeable among different ChAP proteins. In contrast, the N-terminal and the central parts of the ChAPs contribute to cargo specificity. Although the entire N-terminal domain of Chs6p is required for Chs3p export at all cell cycle stages, the central part seems to predominantly favor Chs3p export in small-budded cells. The cargo Chs3p probably also uses a complex motif for the interaction with Chs6, as the C-terminus of Chs3p interacts with Chs6p and is necessary, but not sufficient, for TGN export.
authors.affiliation: Biozentrum, Universität Basel, 4056 Basel, Switzerland.
authors.forename: Uli
authors.initials: U
authors.lastname: Rockenbauch
authors.forename: Alicja M
authors.initials: AM
authors.lastname: Ritz
authors.forename: Carlos
authors.initials: C
authors.lastname: Sacristan
authors.forename: Cesar
authors.initials: C
authors.lastname: Roncero
authors.forename: Anne
authors.initials: A
authors.lastname: Spang
mesh_terms: D020816:Amino Acid Motifs; D002687:Chitin Synthase / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D021601:trans-Golgi Network / Q000378:metabolism / Q000502:physiology*
chemical_list: D029701:Saccharomyces cerevisiae Proteins; C069390:CHS3 protein, S cerevisiae; C491360:CHS5 protein, S cerevisiae; D002687:Chitin Synthase