Structure of the human metapneumovirus polymerase phosphoprotein complex

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• Respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) are significant causes of severe respiratory illness in infants and the elderly.
• Currently, no effective vaccines or antiviral therapies exist to combat these infections.
• The phosphoprotein (P) acts as a vital adaptor in viral genome replication and transcription, bridging the ribonucleoprotein template and the L protein.

Purpose of the Study:

• To elucidate the structural basis of the interaction between the HMPV L protein and its cognate P protein.
• To understand the mechanism by which P facilitates viral RNA synthesis and potentially modulates L protein functions.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to determine the structure of the HMPV L-P complex.
• Detailed structural analysis of the HMPV L protein in complex with a tetramer of P protein.

Main Results:

• A ring-shaped structure of the polymerase and capping domains of HMPV-L bound to P tetramer was resolved.
• The P protein extensively interacts with the N-terminal region of L, burying significant molecular surface area.
• The structure reveals a 'folding-upon-partner-binding' mechanism for P, showcasing its adaptability and role in modulating L functions.

Conclusions:

• The determined structure provides unprecedented insight into the HMPV L-P complex organization and interaction.
• This structural understanding is crucial for deciphering viral replication mechanisms and developing targeted antiviral strategies.
• The findings are expected to accelerate the design of novel antiviral drugs against HMPV and related viruses.