Doyel Sen

Helicases are molecular motor proteins that use the energy of NTP hydrolysis to unidirectionally translocate along nucleic acid while separating the ds DNA strands, removing secondary structures in RNA, and displacing proteins bound to nucleic acids. Helicases are integral parts of the cellular machinery involved in DNA and RNA metabolic processes. Thus, it is not surprising that helicases and helicase-related proteins constitute more than 2% of the eucaryotic genome. Mutations in human genes coding for helicases result in several diseases that result in cancer and premature aging. Helicases also play a key role in viral life cycles such as viral genome replication and genome packaging/unpackaging. Viral helicases are therefore attractive targets for antiviral therapy.
The topic of helicase structure, function, and mechanisms has been widely discussed in the literature. Oligomeric state divides helicases into two groups: ring (hexameric) helicases and all other. This chapter, discusses general mechanisms of translocation and strand separation of nucleic acid by helicases followed by a discussion of the mechanisms of ring helicases.