Unwinding mechanism of SARS-CoV helicase (nsp13) in the presence of Ca 2+ , elucidated by biochemical and single-molecular studies.

The recent outbreak of COVID-19 has created a serious health crisis with fatFal infectious viral diseases, such as Severe Acute Respiratory Syndrome (SARS). The nsp13, a helicase of coronaviruses is an essential element for viral replication that unwinds secondary structures of DNA and RNA, and is thus considered a major therapeutic target for treatment. The replication of coronaviruses and other retroviruses occurs in the cytoplasm of infected cells, in association with viral replication organelles, called virus-induced cytosolic double-membrane vesicles (DMVs). In addition, an increase in cytosolic Ca ²⁺ concentration accelerates viral replication. However, the molecular mechanism of nsp13 in the presence of Ca ²⁺ is not well understood. In this study, we applied biochemical methods and single-molecule techniques to demonstrate how nsp13 achieves its unwinding activity while performing ATP hydrolysis in the presence of Ca ²⁺ . Our study found that nsp13 could efficiently unwind double stranded (ds) DNA under physiological concentration of Ca ²⁺ of cytosolic DMVs. These findings provide new insights into the properties of nsp13 in the range of calcium in cytosolic DMVs.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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