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NMR studies of the structure and dynamics of membrane-bound bacteriophage Pf1 coat protein
1Department of Chemistry, University of Pennsylvania, Philadelphia 19104.
Abstract:
Filamentous bacteriophage coat protein undergoes a remarkable structural transition during the viral assembly process as it is transferred from the membrane environment of the cell, where it spans the phospholipid bilayer, to the newly extruded virus particles. Nuclear magnetic resonance (NMR) studies show the membrane-bound form of the 46-residue Pf1 coat protein to be surprisingly complex with five distinct regions. The secondary structure consists of a long hydrophobic helix (residues 19 to 42) that spans the bilayer and a short amphipathic helix (residues 6 to 13) parallel to the plane of the bilayer. The NH2-terminus (residues 1 to 5), the COOH-terminus (residues 43 to 46), and residues 14 to 18 connecting the two helices are mobile. By comparing the structure and dynamics of the membrane-bound coat protein with that of the viral form as determined by NMR and neutron diffraction, essential features of assembly process can be identified.
Insights
The Pf1 coat protein changes structure dramatically from its membrane-bound form to its viral form. Nuclear magnetic resonance (NMR) studies reveal key insights into this viral assembly process.
Area of Science:
- Structural biology
- Virology
- Biochemistry
Background:
- Filamentous bacteriophage coat proteins transition from membrane-bound to viral forms.
- This transition involves significant structural changes crucial for viral assembly.
Purpose of the Study:
- To elucidate the structural and dynamic properties of the membrane-bound Pf1 coat protein.
- To compare the membrane-bound form with the viral form to understand the assembly mechanism.
Main Methods:
- Nuclear magnetic resonance (NMR) spectroscopy to study the membrane-bound coat protein.
- Comparison with existing NMR and neutron diffraction data for the viral form.
Main Results:
- The membrane-bound 46-residue Pf1 coat protein exhibits a complex structure with five distinct regions.
- Key features include a transmembrane hydrophobic helix, an amphipathic helix, and mobile termini/linker regions.
- NMR studies reveal distinct secondary structures and dynamics in the membrane-bound state.
Conclusions:
- The study identifies essential features of the viral assembly process by comparing membrane-bound and viral coat protein structures.
- Understanding these transitions provides insights into bacteriophage assembly mechanisms.