Late protein

Late protein refers to a category of proteins synthesized during the late phase of the viral replication cycle. These proteins are typically involved in the assembly and release of the virus particles from the host cell. Unlike early proteins, which are produced immediately after the virus enters the cell and are involved in the replication of the viral genome and in the shutdown of the host's DNA synthesis, late proteins are synthesized after the replication of the viral genome has been completed.

Function

The primary function of late proteins is to form the structural components of the virus, including the capsid and the proteins necessary for the virus to attach to and enter new host cells. In some viruses, late proteins also include enzymes that help in the maturation and release of the virus from the host cell. The timing of late protein synthesis ensures that these structural components are produced only when needed, which is after the viral genome has been replicated.

Synthesis

The synthesis of late proteins is tightly regulated by the viral gene expression control mechanisms. In many viruses, the switch from early to late gene expression involves complex interactions between viral proteins, the viral genome, and sometimes host cell factors. This regulation ensures that the virus efficiently uses the host's resources for its replication and assembly.

Examples

In the bacteriophage T4, an example of a virus that infects bacteria, late proteins include those that form the phage head and tail structures, as well as enzymes involved in lysing the bacterial cell to release the newly formed phages. In adenoviruses, which can cause respiratory, intestinal, and eye infections in humans, the fiber proteins that project from the virus particle and are critical for attachment to host cells are expressed late in the infection cycle.

Clinical Significance

Understanding the function and regulation of late proteins is crucial for developing antiviral strategies. Inhibiting the synthesis of these proteins can prevent the assembly and release of new virus particles, thereby limiting the spread of the virus. Research into late proteins also contributes to the development of vaccines, as these structural components are often targets for the immune response.

See Also

• Viral replication
• Viral life cycle
• Protein synthesis
• Gene expression