Sec7 regulatory domains scaffold autoinhibited and active conformations

• 成果类型: Article
• 署名作者: Brownfield, Bryce A.; Richardson, Brian C.; Halaby, Steve L.; Fromme, J. Christopher
• 署名单位: Cornell University; Cornell University; University of Minnesota System; AbbVie
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-15192
• DOI: 10.1073/pnas.2318615121
• 发表日期: 2024-03-01
• 关键词: adp-ribosylation factor; guanine-nucleotide-exchange; arf-gef; cryo-em; saccharomyces-cerevisiae; structural basis; gtpase cascade; g-proteins; golgi; activation

摘要

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 cryogenic electron microscopy 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.