Chapter category: DNA
Essential Molecular Tools for Cellular Machinery Prokaryotic and Eukaryotic DNA Helicases
Chapter authors:
Narendra Tuteja and Renu Tuteja
DNA helicases are ubiquitous molecular motor proteins that harness the chemical free energy of ATP hydrolysis to catalyze the unwinding of energetically stable duplex DNA, and thus play important roles in nearly all aspects of nucleic acid metabolism. Basically helicases break the hydrogen bonds between the duplex helix and move unidirectionally on the bound strand. All the helicases are also translocases and DNA-dependent ATPases. Most of the helicases contain conserved helicase motifs that act as an engine to powers DNA unwinding. Crystal structures have revealed an underlying common structural fold for their function. The genes containing helicase motifs may have evolved from a common ancestor. The minichromosome maintenance (Mcm) protein complex (Mcm4/6/7) provides DNA unwinding function at the origin of replication in all eukaryotes and may act as a licensing factor for DNA replication. The RecQ family of helicases is highly conserved from bacteria to human and is required for the maintenance of genome integrity and also have been implicated in a variety of human genetic disorders. Since the discovery of first DNA helicase from Escherichia coli in 1976, a large number of these enzymes have been isolated from both prokaryotic and eukaryotic systems and the number is still growing. In this review we have covered the historical background of DNA helicases, helicase assays, biochemical properties, helicase motifs, mechanisms of unwinding and translocation, structural information, various functions of DNA helicases, Mcm proteins and the RecQ family of helicases. In addition to these, the properties of nearly all the reported DNA helicases from prokaryotic and eukaryotic systems including viruses and bacteriophages are grouped into several tables.
