AI Article Synopsis
- A novel enzyme called human DNA helicase VI (HDH VI) was isolated from HeLa cells and found to be pure and free of other DNA-related activities.
- It exists as a single unit with a molecular weight of 128 kDa and requires ATP or dATP, along with magnesium ions, to function effectively.
- HDH VI specifically unwinds short DNA duplexes (less than 32 base pairs) and operates unidirectionally from the 3' to 5' end, but does not interact with blunt-end duplexes or RNA-based structures.
Article Abstract
A novel ATP-dependent DNA unwinding enzyme, called human DNA helicase VI (HDH VI), was purified to apparent homogeneity from HeLa cells and characterized. From 327 g of cultured cells, 0.44 mg of pure enzyme was recovered, free of DNA polymerase, ligase, topoisomerase, nicking and nuclease activities. The enzyme behaves as a monomer having an M(r) of 128 kDa, whether determined with SDS-PAGE, or in native conditions. Photoaffinity labelling with [alpha-32P]ATP labelled the 128 kDa protein. Only ATP or dATP hydrolysis supports the unwinding activity for which a divalent cation (Mg2+ > Mn2+) is required. HDH VI unwinds exclusively DNA duplexes with an annealed portion < 32 bp and prefers a replication fork-like structure of the substrate. It cannot unwind blunt-end duplexes and is inactive also on DNA-RNA or RNA-RNA hybrids. HDH VI unwinds DNA unidirectionally by moving in the 3' to 5' direction along the bound strand.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC307051 | PMC |
| http://dx.doi.org/10.1093/nar/23.13.2457 | DOI Listing |
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