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Solution NMR resonance assignment strategies for β-barrel membrane proteins
1Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA.
Protein Science : a Publication of the Protein Society
|June 12, 2013
Summary
This study introduces new methods to assign resonances in beta-barrel membrane proteins, like Opa60. These techniques, including protein cleavage and synthetic peptides, overcome challenges in NMR spectroscopy for better structural determination.
Area of Science:
- Structural Biology
- Biophysics
- Biochemistry
Background:
- Membrane proteins in detergent micelles are challenging for solution NMR due to spectral overlap and line broadening.
- Beta-barrel membrane proteins, crucial for cellular functions, present unique difficulties in structural studies.
- Opa60, an eight-stranded beta-barrel protein from Neisseria gonorrhoeae, serves as a model system with extensive extracellular loops.
Purpose of the Study:
- To develop and implement novel strategies for facilitating resonance assignment in beta-barrel membrane proteins.
- To address spectral overlap and line broadening issues encountered in solution NMR investigations.
- To improve the efficiency and accuracy of structural determination for membrane proteins.
Main Methods:
- Utilized trypsin cleavage to remove extracellular loops, simplifying the NMR spectra of the Opa60 beta-barrel.
- Employed temperature modulation to selectively assign resonances in dynamic loop regions.
- Synthesized a 20 amino acid peptide corresponding to extracellular loop regions for further resonance assignment.
Main Results:
- Achieved 97% resonance assignment for the Opa60 beta-barrel and periplasmic turns after loop removal.
- Successfully assigned 27 loop resonances by modulating temperature, focusing on dynamic regions.
- Assigned 17 loop resonances using a synthetic peptide, demonstrating high spectral overlap with the full-length protein.
Conclusions:
- The combination of trypsin cleavage, temperature modulation, and synthetic peptides significantly enhances resonance assignment for beta-barrel membrane proteins.
- These methods effectively overcome spectral complexities, accelerating solution NMR structure determination.
- The developed strategies offer valuable tools for advancing the study of membrane protein structures and functions.
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