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An NMR sample preparation case study: Considerations for the self-destructive protease caspase-6
Nathanael J Kuzio1, Marco Tonelli2, Jasna Fejzo3
1Department of Chemistry, University of Massachusetts, Amherst, Massachusetts, United States of America.
Abstract:
Proteases represent a difficult family of proteins to purify, concentrate and store at homogeneity due to their toxicity during overexpression and their propensity to self-cleave, leading to the loss of sample stability and function. A protease of interest, caspase-6, is a member of the apoptotic family of caspases, and has been shown to be involved in human neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Previous studies have elucidated key structural aspects and potential inhibition mechanisms of caspase-6 through various structural biology techniques such as x-ray crystallography and hydrogen-deuterium exchange mass spectrometry. However, caspase-6 undergoes a structural transition that requires atomic-resolution insight in solution to understand the conformational transitions and ensemble. This can be most optimally achieved using multi-dimensional biomolecular NMR. Prior attempts to study caspase-6 by NMR have failed due to challenges in sample preparation and insufficient protein concentration. Here, we document our exploratory strategy, which ultimately led to the refinement of crucial sample preparation steps and enabled us to obtain isotopically-labeled caspase-6 in yields suitable for heteronuclear NMR studies. We present this work in the hope that it will assist others in the preparation of difficult protein samples, particularly proteases.
Insights
Researchers optimized sample preparation for caspase-6, a protease involved in neurodegenerative diseases. This breakthrough enables detailed structural studies using nuclear magnetic resonance (NMR) spectroscopy, advancing research on Alzheimer's and Parkinson's disease.
Area of Science:
- Biochemistry
- Structural Biology
- Neuroscience
Background:
- Proteases are challenging to purify and store due to toxicity and self-cleavage.
- Caspase-6, implicated in neurodegenerative diseases like Alzheimer's and Parkinson's, requires atomic-resolution solution studies.
- Previous structural studies of caspase-6 lacked insight into its solution-state conformational transitions.
Purpose of the Study:
- To overcome challenges in preparing caspase-6 for nuclear magnetic resonance (NMR) studies.
- To enable detailed investigation of caspase-6's structural transitions and conformational ensemble in solution.
- To provide a refined sample preparation strategy for difficult-to-study proteases.
Main Methods:
- Exploratory strategy refinement for protein sample preparation.
- Optimization of steps for obtaining isotopically-labeled caspase-6.
- Preparation of sufficient protein concentration for heteronuclear NMR.
Main Results:
- Successful refinement of crucial sample preparation steps for caspase-6.
- Achieved yields of isotopically-labeled caspase-6 suitable for heteronuclear NMR.
- Demonstrated a viable strategy for preparing challenging protease samples.
Conclusions:
- The developed method facilitates high-resolution structural analysis of caspase-6 using NMR.
- This work provides a foundation for understanding caspase-6's role in neurodegenerative diseases.
- The refined protocol can aid researchers in preparing other difficult protein samples, especially proteases.
