Helikase

Helikase, commonly known as helicase, is a class of enzymes that unwind double-stranded nucleic acids, using energy from ATP hydrolysis. They act on DNA or RNA duplexes to separate strands, enabling essential cellular processes such as DNA replication, transcription, repair, recombination, and RNA processing.

Most helicases are motor proteins that translocate along one nucleic acid strand and displace the complementary strand. They are categorized into several superfamilies, with DNA and RNA helicases typically falling into the SF1 and SF2 groups. Many helicases assemble as hexameric rings and move in a directional manner: some unwind in the 5′ to 3′ direction, others in the 3′ to 5′ direction. Structural motifs, including Walker A and B motifs and other catalytic elements, bind and hydrolyze ATP to fuel movement and strand separation.

Biological roles extend across organisms. In bacteria, DnaB functions as a primary replicative helicase, while UvrD participates in DNA repair. In archaea and eukaryotes, the replicative helicase is the MCM2-7 complex, which operates within the CMG complex (Cdc45–MCM2-7–GINS) to unwind DNA at replication forks. Helicases also participate in transcription, DNA repair, and RNA processing by resolving secondary structures and remodeling nucleic acid-protein assemblies. In addition to DNA helicases, RNA helicases such as the DEAD-box family (for example, eIF4A) remodel RNA structures during translation initiation and ribosome assembly.

Clinical relevance includes mutations in helicases linked to genome instability syndromes, such as Bloom syndrome (BLM), Werner syndrome (WRN), and Rothmund-Thomson syndrome (RECQL4). Dysfunctions in helicases are also studied in cancer biology, and helicase inhibitors are explored as potential therapeutic agents.