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15
An evolutionarily conserved protocoatomer-related
complex containing Sec13 and Seh1 dynamically
associates with the vacuole in Saccharomyces cerevisiae
Svetlana Dokudovskaya 1, 8 , Francois Waharte 2 , Avner Schlessinger 3 , Ursula Pieper 3 , Damien
Devos 4 , Ileana Cristea 5 , Rosemary Williams 6 , Jean Salamero 2 , Brian Chait 6 , Andrej Sali 3 , Mark
Field 7 , Michael Rout 6 , Catherine Dargemont 8 .
Institut Gustave Roussy, CNRS UMR8126, Villejuif, France 1 , Institut Curie, CNRS UMR144,
Paris, France 2 , University of California at San Francisco, San Francisco, USA 3 , EMBL,
Heidelberg, Germany 4 , Princeton University, Princeton, USA 5 , The Rockefeller University, New
York, USA 6, University of Cambridge, Cambridge, UK 7 , Institut Jacques Monod, Paris, France 8
Abstract:
The presence of multiple membranous intracellular compartments is a major feature of
eukaryotic cells. Many of the proteins required for formation and maintenance of these
endomembrane systems share an evolutionary history. Retention of identical components,
common secondary and quaternary structure, architecture and function in membrane curvature
support the hypothesis that some membrane coats evolved from a common ancestral
protocoatomer. Here, we identify the SEA (Seh1-associated) protein complex in Saccharomyces
cerevisiae that contains the nucleoporin Seh1 as well as Sec13, a subunit of both the nuclear pore
complex and COPII coated vesicles. In addition to Npr2 and Npr3 (upstream regulators of
TORС1 kinase), the SEA complex also contains four uncharacterized proteins (Sea1-Sea4).
Combined computational and biochemical approaches indicate that the SEA complex proteins
possess structural characteristics similar to components of other membrane coating complexes,
including COPI, COPII, the nuclear pore complex, and the Vps class C complex HOPS/CORVET.
Homologues of SEA complex proteins are well conserved within Opistokhonts, undetectable in
Planta, and only partially retained in other supergroups. The SEA complex dynamically
associates with the vacuole membrane in vivo. Synthetic genetic interaction data and functional
assays suggest a role for the SEA complex in intracellular trafficking, amino acid biogenesis and
response to nitrogen starvation. These data demonstrate that the SEA complex is a new member
of a family of coating assemblies, thus providing additional support for the protocoatomer
model of the endomembrane system evolution.