Relating structure to evolution in class II viral membrane fusion proteins

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• Enveloped viruses require fusion of viral and cellular membranes for genome delivery.
• Viral envelope proteins are responsible for catalyzing this critical membrane fusion event.
• These fusion proteins are classified into at least three distinct structural classes, with Class II proteins possessing a conserved three-domain architecture.

Purpose of the Study:

• To review the structural relationships of newly identified Class II fusion proteins.
• To understand the evolutionary implications of these discoveries on viral fusion mechanisms.

Main Methods:

• Review of structural and sequence data for viral envelope proteins.
• Comparative analysis of Class II fusion proteins from various viral families.
• Phylogenetic analysis to infer evolutionary relationships.

Main Results:

• Class II fusion proteins were previously identified primarily in flaviviruses and alphaviruses.
• In 2013, a Class II fusion protein was discovered in the unrelated phlebovirus genus.
• Two divergent envelope proteins were identified in families containing prototypical Class II proteins, expanding the known diversity.

Conclusions:

• The discovery of Class II fusion proteins in phleboviruses and other divergent proteins significantly alters the understanding of their evolution.
• These findings suggest a more complex evolutionary history for viral membrane fusion machinery than previously recognized.
• The paradigm for Class II fusion protein evolution is shifted by these recent discoveries.