Helicase enzyme that unwinds and separates double-stranded DNA or RNA by breaking the hydrogen bonds between complementary strands. This process is critical for DNA replication , transcription , repair , and recombination .
Key Characteristics: Motor protein : Uses energy from ATP hydrolysis Works in a 5′ → 3′ or 3′ → 5′ direction, depending on the helicase type. Creates single-stranded templates needed for polymerase enzymes . Functions of Helicase: Biological Process Role of Helicase DNA replication Unwinds DNA at the replication fork so DNA polymerase can synthesize new strands. Transcription Helps RNA polymerase access the DNA template. DNA repair Unwinds damaged regions to allow repair enzymes access. Recombination Assists in separating DNA strands during genetic exchange.
Examples of Helicases: Organism/Context Helicase Name Function E. coli DnaB helicase Main helicase at the bacterial replication fork Humans MCM complex Helicase complex that unwinds DNA during replication NER pathwayXPB and XPD (part of TFIIH)Unwind DNA around damage sites in nucleotide excision repair RNA processes DDX family helicases Involved in RNA splicing, translation, and transport
Mechanism of Action: Helicase binds to DNA at the replication origin or repair site.It uses ATP hydrolysis to power movement along one strand. As it moves, it breaks hydrogen bonds between base pairs. This opens the DNA double helix , forming single-stranded regions . Clinical Relevance: Werner syndrome and Bloom syndrome : Caused by mutations in human DNA helicases, leading to premature aging and genomic instability .Cancer replication stress and mutations , contributing to cancer development.Antiviral targets : Viral helicases (e.g., in hepatitis C, SARS-CoV-2) are drug targets for antiviral therapies.Summary Table: Property Description Type of Enzyme ATP-dependent motor protein Substrate DNA or RNA Action Unwinds double-stranded nucleic acids Key Processes Replication, transcription, repair, recombination Directionality 5′→3′ or 3′→5′ depending on helicase Clinical Importance Linked to aging disorders, cancer, and antiviral drug targets
