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The structures of exocyst subunit Exo70p and the Exo84p C-terminal domains reveal a common motif

Abstract

The exocyst is a large complex that is required for tethering vesicles at the final stages of the exocytic pathway in all eukaryotes. Here we present the structures of the Exo70p subunit of this complex and of the C-terminal domains of Exo84p, at 2.0-Å and 2.85-Å resolution, respectively. Exo70p forms a 160-Å-long rod with a novel fold composed of contiguous α-helical bundles. The Exo84p C terminus also forms a long rod (80 Å), which unexpectedly has the same fold as the Exo70p N terminus. Our structural results and our experimental observations concerning the interaction between Exo70p and other exocyst subunits or Rho3p GTPase are consistent with an architecture wherein exocyst subunits are composed of mostly helical modules strung together into long rods.

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Figure 1: Exo70p is a long rod composed of contiguous α-helical bundles.
Figure 2: Domain C of Exo70p is necessary for mediating the nucleotide-sensitive interaction with Rho3p.
Figure 3: Exo70p interacts with several exocyst components.
Figure 4: Exo70p shows different interactions with Sec6p, Sec8p and Sec10p.
Figure 5: The structure of the Exo84p C terminus is similar to that of the Exo70p N terminus.
Figure 6: Schematic showing an exocyst subcomplex modeled from elongated subunits, consisting of α-helical modules strung end to end.

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Acknowledgements

We are grateful to the staffs at beamlines X25 and X29 at Brookhaven National Laboratory and at the NE-CAT beamline 8BM at the APS for their help in collecting data. P. Patel was helpful in the initial characterization of Exo70p. We are very grateful to D.W. Rodgers and G. Warren for discussion and their comments regarding this manuscript, to M. Munson for allowing us to cite her structure of Sec6p and to F. Quiocho for sharing with us the manuscript describing the Sec15 structure. K.M.R. is supported by funds from the G. Harold and Leila Y. Mathers Foundation and the Pew Charitable Trust, P.N. is funded by grant GM35370 from the US National Institutes of Health and G.D. and A.H.H. have been supported by fellowships from the American Heart Foundation and the Anna Fuller Fund, respectively.

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Correspondence to Peter Novick or Karin M Reinisch.

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Supplementary information

Supplementary Fig. 1

The carboxy-terminal fragment of Sec15 is composed of helical modules strung into a rod, like Exo70p. (PDF 948 kb)

Supplementary Fig. 2

Sequence alignment for the Exo70p C-terminus. (PDF 250 kb)

Supplementary Fig. 3

Sequence alignment of the S. cerevisiae (Sc) Exo84p carboxy-terminal domains. (PDF 446 kb)

Supplementary Table 1

Exo70p truncation constructs (PDF 34 kb)

Supplementary Table 2

Secondary structure and coiled-coil prediction for S. cerevisiae exocyst subunits (PDF 94 kb)

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Dong, G., Hutagalung, A., Fu, C. et al. The structures of exocyst subunit Exo70p and the Exo84p C-terminal domains reveal a common motif. Nat Struct Mol Biol 12, 1094–1100 (2005). https://doi.org/10.1038/nsmb1017

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