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Virologie

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Viral helicases : a new class of enzymes Volume 2, issue 6, Novembre - Décembre 1998

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Helicases are a class of enzymes capable of unwinding duplex regions of nucleic acids by disrupting the hydrogen bonds using the energy generated from the hydrolysis of a nucleoside 5’-triphosphate. DNA helicases were first described some 20 years ago and thereafter extensively studied. On the other hand, RNA helicases have only recently been identified ; they occur in a wide spectrum of organisms comprising viruses, bacteria, yeast, and humans. Putative viral RNA helicases identified based on computer-assisted sequence homologies, are present in a large number of virus families, with the notable exceptions of retroviruses and negative strand RNA viruses. Theoretical predictions of helicases have been corroborated by biochemical studies in the case of several viruses, and will be discussed here. However, for other viruses, such studies have so far failed to confirm the postulated function, and the question still remains as to whether all viruses need a helicase.