Defined Subunit Arrangement and Rab Interactions Are Required for Functionality of the HOPS Tethering Complex

Authors

  • Clemens W. Ostrowicz,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
    2. Present address: Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
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    • These authors contributed equally to this work.

  • Cornelia Bröcker,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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    • These authors contributed equally to this work.

  • Franziska Ahnert,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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  • Mirjana Nordmann,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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  • Jens Lachmann,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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  • Karolina Peplowska,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
    2. Present address: Max-Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
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  • Angela Perz,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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  • Kathrin Auffarth,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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  • Siegfried Engelbrecht-Vandré,

    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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  • Christian Ungermann

    Corresponding author
    1. Department of Biology, Biochemistry Section, University of Osnabrück, Barbarastrasse 13, 49076 Osnabrück, Germany
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Christian Ungermann, christian.ungermann@biologie.uni-osnabrueck.de

Abstract

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.

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