viral protein processing

Definition

Target type: biologicalprocess

Any protein maturation process achieved by the cleavage of a peptide bond or bonds within a viral protein. [GOC:bf, GOC:jl, ISBN:0781702534]

Viral protein processing is a crucial step in the viral life cycle, enabling the production of functional viral proteins from precursor polyproteins. This complex process involves a series of enzymatic cleavages, often carried out by viral proteases, which break down the polyprotein into individual proteins. The precise mechanism and enzymes involved vary significantly among different viral families.

**1. Translation and Polyprotein Synthesis:**
- Viral mRNA is translated by host ribosomes, producing a single large polypeptide chain known as a polyprotein.
- The polyprotein contains multiple viral protein domains, arranged in a specific order.

**2. Viral Protease Activity:**
- Viral proteases, encoded by the viral genome, are responsible for cleaving the polyprotein.
- These proteases exhibit high specificity, recognizing unique amino acid sequences within the polyprotein.
- Some viral proteases are autocatalytic, meaning they cleave themselves from the polyprotein.

**3. Cleavage Events and Protein Maturation:**
- Viral proteases cleave the polyprotein at specific sites, releasing individual proteins.
- The order of cleavage events can be sequential or simultaneous, depending on the viral family.
- Cleavage can occur at both the N-terminus and C-terminus of the polyprotein.

**4. Protein Folding and Assembly:**
- Once released, individual proteins fold into their correct three-dimensional structures.
- Some proteins may associate with other viral proteins to form functional complexes.
- These protein complexes are essential for various aspects of the viral life cycle, including replication, assembly, and host cell interaction.

**5. Examples of Viral Proteases and Their Targets:**
- **HIV-1 protease:** Cleaves the Gag-Pol polyprotein, generating mature viral proteins essential for virion assembly.
- **Hepatitis C virus (HCV) protease:** Cleaves the polyprotein, releasing viral proteins involved in replication and assembly.
- **Poliovirus protease:** Cleaves the polyprotein, generating proteins required for RNA replication and capsid formation.

**6. Regulation of Viral Protein Processing:**
- Viral protein processing is tightly regulated to ensure the production of functional viral proteins at the appropriate time and location.
- This regulation involves factors such as the availability of viral proteases, the timing of translation, and the cellular environment.

**7. Therapeutic Implications:**
- Viral proteases are attractive targets for antiviral drug development.
- Inhibitors of viral proteases can block viral protein processing, preventing viral replication.
- Examples include antiretroviral drugs such as saquinavir and ritonavir, which target HIV-1 protease.

In summary, viral protein processing is a complex and essential step in the viral life cycle, involving precise enzymatic cleavages that generate functional viral proteins. This process is a critical target for antiviral drug development.'
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Proteins (26)

Compounds (412)