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Auto-regulation of Rab5 GEF activity in Rabex5 by allosteric structural changes, catalytic core dynamics and
Janelle Lauer1, Sandra Segeletz1, Alice Cezanne1
1Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
Elife
|November 14, 2019
Summary
Rabex5, a regulator of intracellular trafficking, is more complexly auto-regulated than previously thought. Ubiquitin binding not only positions Rabex5 but also allosterically controls its Rab5 guanine exchange factor (GEF) activity.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Intracellular trafficking relies on Rab GTPases, regulated by guanine exchange factors (GEFs).
- Rabex5, a Rab5 GEF, was previously thought to be auto-inhibited by its C-terminus.
Purpose of the Study:
- To investigate the auto-regulation mechanisms of Rabex5 and its interaction with Rabaptin5.
- To elucidate the role of Rabex5's domains in its catalytic activity.
Main Methods:
- Hydrogen deuterium exchange mass spectrometry (HDX-MS) was used to study Rabex5 and Rabaptin5 proteins.
- Chemical cross-linking mass spectrometry and integrative modeling generated a structural model of Rabex5.
- Nucleotide exchange activity was correlated with structural changes in Rabex5 constructs.
Main Results:
- New auto-regulatory roles for ubiquitin binding domains and the linker region of Rabex5 were identified.
- Enhanced dynamics in Rabex5's catalytic core were linked to its GEF activity.
- Ubiquitin binding was shown to allosterically control Rab5 GEF activity.
Conclusions:
- Rabex5 exhibits a more complex auto-regulation mechanism than previously understood.
- Ubiquitin binding plays a dual role in positioning Rabex5 and modulating its GEF activity.
- Structural dynamics are crucial for the catalytic function of Rabex5.
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