Purification and properties of human DNA helicase VI

Tuteja, Narendra ; ochem, Alexander ; Taneja, Poonam ; Tuteja, Renu ; Skopac', Doris ; Falaschi, Arturo (1995) Purification and properties of human DNA helicase VI Nucleic Acids Research, 23 (13). pp. 2457-2463. ISSN 0305-1048

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Official URL: http://nar.oxfordjournals.org/content/23/13/2457.a...

Related URL: http://dx.doi.org/10.1093/nar/23.13.2457


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, llgase, topoisomerase, nicking and nuclease activities. The enzyme behaves as a monomer having an Mr of 128 kDa, whether determined with SDS-PAGE, or in native conditions. Photoaffinlty labelling wfth [α−32PJATP 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 RNARNA hybrids. HDH VI unwinds DNA unidirectionally by moving In the 3' to 5' direction along the bound strand.

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