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Function and solution structure of the Arabidopsis thaliana RALF8 peptide
Ronnie O Frederick1, Miyoshi Haruta2, Marco Tonelli1
1National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, Wisconsin, 53706.
Protein Science : a Publication of the Protein Society
|April 21, 2019
Summary
Researchers successfully produced and characterized plant peptides, rapid alkalinization factors (RALFs), using recombinant methods. RALF8 showed biological activity and a stable structure, while RALF1 aggregated, highlighting differences in their recombinant preparation and properties.
Area of Science:
- Biochemistry
- Molecular Biology
- Plant Science
Background:
- Rapid alkalinization factors (RALFs) are small, secreted peptides involved in plant growth and development.
- Understanding the structure-function relationship of RALFs is crucial for deciphering their roles in plant signaling pathways.
Purpose of the Study:
- To recombinantly prepare and characterize two related RALF peptides, RALF1 and RALF8.
- To investigate the structural and biological properties of RALF8 using nuclear magnetic resonance (NMR) spectroscopy.
- To compare the recombinant preparation and properties of RALF1 and RALF8.
Main Methods:
- Recombinant expression of RALF1 and RALF8 in Escherichia coli.
- Purification of peptides and preparation of isotopically labeled samples (15N, 13C).
- Nuclear magnetic resonance (NMR) spectroscopy for structural analysis, including assignment and disulfide pairing determination.
- Assessment of biological activity through interaction with plant receptor kinases and in vivo root growth assays.
Main Results:
- Recombinant RALF8 was purified and exhibited well-resolved NMR spectra, indicating a stable structure.
- RALF8 demonstrated biological activity, including interaction with a plant receptor kinase, calcium mobilization, and root growth suppression.
- Recombinant RALF1, isolated with an N-terminal His-tag, showed poor NMR spectra indicative of aggregation.
- The solution structure of RALF8 revealed it to be mostly disordered, with ordered loops formed by disulfide bridges.
Conclusions:
- RALF8 can be successfully prepared recombinantly and possesses defined structural and biological characteristics.
- RALF1's recombinant preparation presents challenges due to aggregation, impacting its structural and functional analysis.
- The study provides insights into the structural basis of RALF peptide function and differential behavior during recombinant expression.
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