Replicase

Replicase
File:RNA polymerase.png Structure of RNA-dependent RNA polymerase
Identifiers
EC number	2.7.7.48
CAS number	9014-25-5
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

Replicase is a type of enzyme that catalyzes the replication of RNA from an RNA template. It is a crucial component in the life cycle of RNA viruses, where it is often referred to as RNA-dependent RNA polymerase (RdRp). This enzyme is responsible for copying the viral RNA genome, allowing the virus to reproduce within a host cell.

Structure and Function

Replicases are typically large, multi-subunit complexes that can vary significantly in structure between different types of viruses. The core function of replicase is to synthesize a complementary RNA strand from an RNA template, a process that is essential for viral replication.

Mechanism of Action

The replicase enzyme binds to the RNA template and uses it as a guide to synthesize a new RNA strand. This process involves the addition of ribonucleotides to the growing RNA chain, which are complementary to the template strand. The enzyme moves along the template, reading the sequence and catalyzing the formation of phosphodiester bonds between nucleotides.

Role in Viral Replication

In the context of RNA viruses, replicase is responsible for both the replication of the viral genome and the transcription of viral mRNA. This dual role is critical for the production of viral proteins and the assembly of new viral particles.

Types of Replicase

Replicases can be classified based on the type of RNA virus they are associated with:

• Positive-sense RNA viruses: These viruses have genomes that can be directly translated into proteins. The replicase in these viruses synthesizes a complementary negative-sense RNA strand, which then serves as a template for producing more positive-sense RNA genomes.

• Negative-sense RNA viruses: These viruses have genomes that are complementary to the mRNA. The replicase synthesizes a positive-sense RNA strand from the negative-sense genome, which can then be translated into proteins or used as a template for genome replication.

• Double-stranded RNA viruses: These viruses have genomes consisting of double-stranded RNA. The replicase in these viruses is responsible for unwinding the double-stranded RNA and synthesizing new RNA strands.

Clinical Significance

Replicase is a target for antiviral drugs, as inhibiting this enzyme can prevent the replication of RNA viruses. For example, drugs that target the replicase of the Hepatitis C virus have been developed to treat infections by this virus.

Research and Developments

Recent advances in structural biology have provided detailed insights into the structure and function of replicase enzymes. These studies have facilitated the development of novel antiviral therapies that specifically target the replicase of various RNA viruses.

Also see

• RNA polymerase
• Reverse transcriptase
• Viral replication
• Antiviral drug