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Enzyme-catalyzed DNA unwinding. A DNA-dependent ATPase from E. coli
The Journal of Biological Chemistry
|December 10, 1979
Summary
Researchers isolated a novel DNA-dependent ATPase from E. coli, named helicase III. This enzyme hydrolyzes ATP using single-stranded DNA and facilitates DNA strand separation.
Area of Science:
- Molecular Biology
- Enzymology
Background:
- The study focuses on enzymes involved in DNA metabolism.
- Previous research identified two DNA strand separation proteins in E. coli: helicase I and helicase II.
Purpose of the Study:
- To isolate and characterize a new DNA-dependent ATPase from E. coli.
- To determine the enzymatic activity and properties of the novel protein.
Main Methods:
- Purification of the enzyme from E. coli.
- Enzymatic assays to measure ATP hydrolysis.
- Analysis of cofactor requirements and reaction products.
- Assessment of DNA strand separation activity.
Main Results:
- A new DNA-dependent ATPase was purified to over 90% purity.
- The enzyme consists of two identical 20,000 molecular weight polypeptide chains.
- It hydrolyzes ATP in the presence of single-stranded DNA (but not double-stranded DNA), producing ADP and Pi.
- The enzyme, in conjunction with E. coli DNA binding protein and ATP, promotes the strand separation of duplex DNA.
Conclusions:
- The novel enzyme functions as a DNA helicase.
- This protein is designated as helicase III, expanding the known repertoire of DNA strand separation enzymes in E. coli.