capsida

Capsida, also known as capsid, is a protein shell that surrounds and protects the genetic material of certain viruses. It is a common structural component found in many types of viruses, including bacteriophages, which infect bacteria, and some plant and animal viruses. The capsid is typically composed of multiple copies of a single protein or a few different proteins, arranged in a symmetrical pattern to form a protective coat around the viral genome.

The structure and composition of capsids vary widely among different viruses. Some capsids are simple, consisting of a single type of protein, while others are complex, composed of multiple protein types arranged in intricate patterns. The capsid's primary function is to protect the viral genome from the host's defenses and to facilitate the entry of the virus into a new host cell. Once inside the host cell, the capsid is often disassembled, releasing the viral genome to begin the process of viral replication.

Capsids can also play a role in viral morphogenesis, the process by which a virus assembles its components into an infectious particle. In some cases, the capsid may also contain enzymes or other proteins that contribute to viral replication or pathogenesis.

The study of capsids is an active area of research in virology, as understanding the structure and function of these protein shells can provide insights into viral pathogenesis, the development of antiviral therapies, and the evolution of viruses. Techniques such as cryo-electron microscopy and X-ray crystallography are commonly used to study the three-dimensional structure of capsids at high resolution.