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Recombinant Protein Expression, Crystallization, and Biophysical Studies of a Bacillus-conserved Nucleotide Pyrophosphorylase, BcMazG
Published on: May 16, 2017
Crystallization and Biophysical Approaches for Studying the Interactions Between the Vps4-MIT Domain and ESCRT-III
Takayuki Obita1, Rieko Kojima2,3, Mineyuki Mizuguchi2
1Faculty of Pharmaceutical Sciences, University of Toyama, Toyama, Japan. obita@pha.u-toyama.ac.jp.
Abstract:
The AAA ATPase Vps4 disassembles the ESCRT complex from the endosomal membrane. Vps4 contains an N-terminal MIT (microtubule interacting and transport) domain and a C-terminal catalytic domain. The MIT domain binds to MIMs (MIT-interacting motifs), which exist at the C-terminus of ESCRT-III proteins, with a dissociation constant in the micromolar range. Five MIMs have been identified by structural and biophysical methods to date, and the recognition motifs have been refined. Among biophysical approaches used to analyze protein interactions, surface plasmon resonance (SPR) analysis is often suitable for weak interactions, and fluorescence-binding assay has an advantage in terms of sensitivity. We have introduced protein modification tags into the N-terminus of proteins with bacterial expression vectors for biotinylation and FlAsH (fluorescein arsenical hairpin binder) fluorescent labeling. Here, we describe how to purify the MIT domain of Vps4 and the MIMs of ESCRT-III proteins and how to conduct crystallography, SPR, and fluorescence-binding assays.
Insights
The AAA ATPase Vps4 disassembles ESCRT complexes. This study details methods to purify Vps4 MIT domains and ESCRT-III MIMs for biophysical analysis of their weak interactions using SPR and fluorescence assays.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- The AAA ATPase Vps4 is crucial for disassembling ESCRT complexes from endosomal membranes.
- Vps4 possesses an N-terminal MIT domain that interacts with MIMs on ESCRT-III proteins.
- These interactions are essential for cellular trafficking and are characterized by low micromolar dissociation constants.
Purpose of the Study:
- To establish protocols for purifying the Vps4 MIT domain and ESCRT-III MIMs.
- To describe the application of surface plasmon resonance (SPR) and fluorescence-binding assays for characterizing these weak protein-protein interactions.
- To provide a foundation for further structural and biophysical investigations of the ESCRT machinery.
Main Methods:
- Bacterial expression of Vps4 MIT domain and ESCRT-III MIMs with N-terminal modification tags (biotinylation, FlAsH).
- Protein purification strategies for both interacting partners.
- Surface Plasmon Resonance (SPR) for analyzing binding kinetics and affinity.
- Fluorescence-binding assays for sensitive detection of molecular interactions.
- Crystallography for structural determination of the Vps4 MIT domain and MIM complexes.
Main Results:
- Successful purification of recombinant Vps4 MIT domain and various ESCRT-III MIM peptides.
- Demonstration of Vps4 MIT domain binding to ESCRT-III MIMs using SPR and fluorescence assays.
- Characterization of the binding affinity, revealing dissociation constants in the micromolar range.
- Establishment of protocols amenable to structural studies via crystallography.
Conclusions:
- The described methods enable robust purification and biophysical characterization of Vps4 MIT-MIM interactions.
- These techniques are valuable for studying weak protein-protein interactions relevant to ESCRT complex function.
- The findings facilitate deeper structural and mechanistic understanding of endosomal sorting and viral budding processes.
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