DNA Helicases
This extract was created in the absence of an abstract.
Excerpt
Enzymes capable of unwinding double-stranded DNA have been isolated from bacteria, bacteriophage-infected cells, and plant cells. The enzymes require a supply of ATP for activity, they are DNA-dependent ATP-γ-phosphohydrolases, and they bind specifically to the single-stranded form of DNA. With some of these enzymes—recBC nuclease (Mac-Kay and Linn 1976) and Escherichia coli rep protein (Denhardt et al. 1972; Scott et al. 1977)—chain separation is achieved only in the presence of a DNA-binding protein. An enzyme purified from the meiotic cells of Lilium opens the terminal nucleotide base pairs of a duplex but does not separate the strands further (Hotta and Stern 1978). The three enzymes discussed here are capable of dissociating a duplex completely into single strands independently of DNA-binding proteins. These enzymes (called DNA helicases), previously characterized physically and chemically in our laboratory, have been subjected to a comparative study.
The enzymes are DNA helicase I (m.w. 180,000) isolated...
