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Published on: February 10, 2022
Determination of Dissociation Constants for the Interaction of Myosin-5a with its Cargo Protein Using Microscale
Rui Zhou1,2, Jiabin Pan1,2, Xiang-Dong Li1,2
1Group of Cell Motility and Muscle Contraction, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
Abstract:
Myosin-5a (Myo5a) is an actin-dependent molecular motor that recognizes a diverse range of cargo proteins through its tail domain, playing a crucial role in the transport and localization of various organelles within the cell. We have identified a new interaction between Myo5a and its cargo protein melanophilin (Mlph), i.e., the interaction between the middle tail domain of Myo5a (Myo5a-MTD) and the actin-binding domain of Mlph (Mlph-ABD), by GST pulldown assay. We then intend to obtain the dissociation constant between Myo5a-MTD and Mlph-ABD using isothermal titration calorimetry (ITC) or microscale thermophoresis (MST), both of which are two commonly used methods for determining quantitative data on protein interactions. The advantages of MST over ITC include less protein usage, shorter operation time, and higher sensitivity. In this protocol, we present a method for using MST to determine the dissociation constants of Myo5a-MTD and Mlph-ABD, which were purified through overexpression in bacteria using affinity chromatography. The dissociation constant values obtained directly reflect the binding strength between these two proteins and provide a foundation for the isolation and purification of the complex in the future. Key features • A protocol for determining the dissociation constants between two purified proteins using microscale thermophoresis (MST). • Detailed procedures for purification of recombinant proteins expressed in E. coli.
Insights
We identified a new interaction between Myosin-5a (Myo5a) and melanophilin (Mlph). This study details a microscale thermophoresis (MST) method to quantify the binding strength of these crucial motor proteins.
Area of Science:
- Cellular biology
- Molecular motors
- Protein-protein interactions
Background:
- Myosin-5a (Myo5a) is an actin-dependent molecular motor essential for intracellular transport.
- Myo5a utilizes its tail domain to bind diverse cargo proteins, including melanophilin (Mlph).
- Understanding Myo5a-Mlph interaction is key to elucidating organelle transport mechanisms.
Purpose of the Study:
- To identify and characterize the interaction between Myosin-5a middle tail domain (Myo5a-MTD) and melanophilin actin-binding domain (Mlph-ABD).
- To establish a protocol for quantifying the binding affinity (dissociation constant) between Myo5a-MTD and Mlph-ABD using microscale thermophoresis (MST).
Main Methods:
- Protein-protein interaction identified via GST pulldown assay.
- Recombinant Myo5a-MTD and Mlph-ABD proteins purified through bacterial overexpression and affinity chromatography.
- Dissociation constants determined using microscale thermophoresis (MST).
Main Results:
- A novel interaction was confirmed between Myo5a-MTD and Mlph-ABD.
- Microscale thermophoresis (MST) was successfully employed to measure the dissociation constants.
- The dissociation constant quantifies the binding strength between Myo5a and Mlph.
Conclusions:
- The developed MST protocol provides a sensitive and efficient method for determining protein-protein binding affinities.
- Quantified binding strength data serves as a foundation for future studies on Myo5a-Mlph complex isolation and function.
- This research contributes to understanding the molecular mechanisms underlying Myo5a-mediated cargo transport.
