Sec7 regulatory domains scaffold autoinhibited and active conformations

Brownfield, B. A.; Richardson, B. C.; Halaby, S. L.; Fromme, J. C.

doi:10.1101/2023.11.22.568272

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bioRxiv · 10.1101/2023.11.22.568272

Sec7 regulatory domains scaffold autoinhibited and active conformations

Brownfield, B. A.·Richardson, B. C.·Halaby, S. L.·Fromme, J. C.

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Abstract

The late stages of Golgi maturation involve a series of sequential trafficking events in which cargo-laden vesicles are produced and targeted to multiple distinct subcellular destinations. Each of these vesicle biogenesis events requires activation of an Arf GTPase by the Sec7/BIG guanine nucleotide exchange factor (GEF). Sec7 localization and activity is regulated by autoinhibition, positive feedback, and interaction with other GTPases. Although these mechanisms have been characterized biochemically, we lack a clear picture of how GEF localization and activity is modulated by these signals. Here we report the cryoEM structure of full-length Sec7 in its autoinhibited form, revealing the architecture of its multiple regulatory domains. We use functional experiments to determine the basis for autoinhibition and use structural predictions to produce a model for an active conformation of the GEF that is supported empirically. This study therefore elucidates the conformational transition that Sec7 undergoes to become active on the organelle membrane surface.

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Brownfield, B. A., Richardson, B. C., Halaby, S. L., Fromme, J. C.. 2023-11-22. Sec7 regulatory domains scaffold autoinhibited and active conformations. https://doi.org/10.1101/2023.11.22.568272

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