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Structure and dynamics of the Pf1 filamentous bacteriophage coat protein in micelles
Abstract:
The major coat protein of filamentous bacteriophage adopts its membrane-bound conformation in detergent micelles. High-resolution 1H and 15N NMR experiments are used to characterize the structure and dynamics of residues 30-40 in the hydrophobic midsection of Pf1 coat protein in sodium dodecyl sulfate micelles. Uniform and specific-site 15N labels enable the immobile backbone sites to be identified by their 1H/15N heteronuclear nuclear Overhauser effect and allow the assignment of 1H and 15N resonances. About one-third of the amide N-H protons in the protein undergo very slow exchange with solvent deuterons, which is indicative of sites in highly structured environments. The combination of results from 1H/15N heteronuclear correlation, 1H homonuclear correlation, and 1H homonuclear Overhauser effect experiments assigns the resonances to specific residues and demonstrates that residues 30-40 of the coat protein have a helical secondary structure.
Insights
This study used nuclear magnetic resonance (NMR) to analyze the Pf1 coat protein in detergent micelles. Results reveal a helical secondary structure in residues 30-40, indicating a membrane-bound conformation.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biophysics
Background:
- Filamentous bacteriophage coat proteins are crucial for viral structure and assembly.
- Understanding their membrane-bound conformation is key to viral infection mechanisms.
- Detergent micelles serve as a model system for studying membrane protein interactions.
Purpose of the Study:
- To elucidate the high-resolution structure and dynamics of the Pf1 coat protein's hydrophobic midsection.
- To characterize the protein's conformation within a membrane-mimicking environment (sodium dodecyl sulfate micelles).
- To identify structured regions and assign specific resonances within the protein.
Main Methods:
- High-resolution 1H and 15N Nuclear Magnetic Resonance (NMR) spectroscopy.
- Utilized uniform and specific-site 15N labeling for enhanced spectral analysis.
- Employed heteronuclear and homonuclear correlation experiments (including NOE) for resonance assignment and structural determination.
Main Results:
- Identified immobile backbone sites using 1H/15N heteronuclear nuclear Overhauser effect (NOE).
- Observed very slow amide N-H proton exchange, indicating highly structured environments.
- Assigned resonances and demonstrated helical secondary structure in residues 30-40 of the coat protein.
Conclusions:
- The hydrophobic midsection of Pf1 coat protein adopts a helical conformation in sodium dodecyl sulfate micelles.
- This helical structure is consistent with the protein's membrane-bound state.
- NMR provides detailed insights into the structural dynamics of viral coat proteins in model membrane environments.