A viral capsid protein is a structural protein that forms the capsid, which is the protein shell enclosing and protecting the genetic material (DNA or RNA) of a virus. The capsid plays a critical role in the viral life cycle and is essential for infectivity.
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Composition:
- Capsids are typically composed of repeating units of capsid proteins, which self-assemble into highly symmetrical structures.
- The arrangement can be icosahedral, helical, or more complex, depending on the virus.
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Functions:
- Protection: Shields the viral genome from degradation by enzymes (nucleases) or environmental factors.
- Host Interaction: Facilitates attachment to host cells by interacting with specific receptors, enabling viral entry.
- Genome Delivery: Assists in delivering the viral genome into the host cell, often by disassembling or rearranging during infection.