Molecular architecture of the TRAPPII complex and implications for vesicle tethering.
Multisubunit tethering complexes participate in the process of vesicle tethering--the initial interaction between transport vesicles and their acceptor compartments. TRAPPII (named for transport protein particle II) is a highly conserved tethering complex that functions in the late Golgi apparatus and consists of all of the subunits of TRAPPI and three additional, specific subunits. We have purified native yeast TRAPPII and characterized its structure and subunit organization by single-particle EM. Our data show that the nine TRAPPII components form a core complex that dimerizes into a three-layered, diamond-shaped structure. The TRAPPI subunits assemble into TRAPPI complexes that form the outer layers. The three TRAPPII-specific subunits cap the ends of TRAPPI and form the middle layer, which is responsible for dimerization. TRAPPII binds the Ypt1 GTPase and probably uses the TRAPPI catalytic core to promote guanine nucleotide exchange. We discuss the implications of the structure of TRAPPII for coat interaction and TRAPPII-associated human pathologies.
Yip
Calvin K
CK
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA. calvin_yip@hms.harvard.edu
Berscheminski
Julia
J
Walz
Thomas
T
D019281:Dimerization; D006056:Golgi Apparatus / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism
D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; C080595:TRS65 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C060755:YPT1 protein, S cerevisiae; D020691:rab GTP-Binding Proteins