Defined subunit arrangement and rab interactions are required for functionality of the HOPS tethering complex.
Within the endomembrane system of eukaryotic cells, multisubunit tethering complexes together with their corresponding Rab-GTPases coordinate vesicle tethering and fusion. Here, we present evidence that two homologous hexameric tethering complexes, the endosomal CORVET (Class C core vacuole/endosome transport) and the vacuolar HOPS (homotypic vacuole fusion and protein sorting) complex, have similar subunit topologies. Both complexes contain two Rab-binding proteins at one end, and the Sec1/Munc18-like Vps33 at the opposite side, suggesting a model on membrane bridging via Rab-GTP and SNARE binding. In agreement, HOPS activity can be reconstituted using purified subcomplexes containing the Rab and Vps33 module, but requires all six subunits for activity. At the center of HOPS and CORVET, the class C proteins Vps11 and Vps18 connect the two parts, and Vps11 binds both HOPS Vps39 and CORVET Vps3 via the same binding site. As HOPS Vps39 is also found at endosomes, our data thus suggest that these tethering complexes follow defined but distinct assembly pathways, and may undergo transition by simple subunit interchange.
Ostrowicz
Clemens W
CW
Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany.
Bröcker
Cornelia
C
Ahnert
Franziska
F
Nordmann
Mirjana
M
Lachmann
Jens
J
Peplowska
Karolina
K
Perz
Angela
A
Auffarth
Kathrin
K
Engelbrecht-Vandré
Siegfried
S
Ungermann
Christian
C
D011992:Endosomes / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000737:chemistry / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*
D044385:GTP-Binding Protein alpha Subunits; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins