Structural Model of Bacteriophage P22 Scaffolding Protein in a Procapsid by Magic-Angle Spinning NMR

Area of Science:

• Virology
• Structural Biology
• Biochemistry

Background:

• Icosahedral dsDNA viruses utilize scaffolding proteins for procapsid formation during assembly.
• Bacteriophage P22 scaffolding protein (SP) is essential for T=7 icosahedral procapsid assembly but its structure is largely unknown.

Purpose of the Study:

• To determine the structural model of P22 scaffolding protein within the procapsid.
• To elucidate the oligomeric state and secondary structure of P22 SP in situ.

Main Methods:

• Magic Angle Spinning (MAS) NMR spectroscopy, including CPMAS CryoProbe for enhanced sensitivity.
• ¹⁹F MAS NMR experiments to investigate protein oligomerization.

Main Results:

• A structural model of P22 scaffolding protein within the 23 MDa procapsid was determined.
• P22 SP exhibits both α-helical and disordered segments.
• The scaffolding protein forms a trimer of dimers when associated with the procapsid lattice.

Conclusions:

• This study provides the first structural insights into P22 SP beyond its C-terminal helix-turn-helix.
• MAS NMR is a powerful technique for studying viral protein assemblies inaccessible to other methods.