title: Demonstration of helicase activity in the nonstructural protein, NSs, of the negative-sense RNA virus, groundnut bud necrosis virus.
abstract: The nonstructural protein NSs, encoded by the S RNA of groundnut bud necrosis virus (GBNV) (genus Tospovirus, family Bunyaviridae) has earlier been shown to possess nucleic-acid-stimulated NTPase and 5' α phosphatase activity. ATP hydrolysis is an essential function of a true helicase. Therefore, NSs was tested for DNA helicase activity. The results demonstrated that GBNV NSs possesses bidirectional DNA helicase activity. An alanine mutation in the Walker A motif (K189A rNSs) decreased DNA helicase activity substantially, whereas a mutation in the Walker B motif resulted in a marginal decrease in this activity. The parallel loss of the helicase and ATPase activity in the K189A mutant confirms that NSs acts as a non-canonical DNA helicase. Furthermore, both the wild-type and K189A NSs could function as RNA silencing suppressors, demonstrating that the suppressor activity of NSs is independent of its helicase or ATPase activity. This is the first report of a true helicase from a negative-sense RNA virus.
authors: Department of Biochemistry, New Biological Sciences, Indian Institute of Science, Bangalore, 560012, Karnataka, India.
authors: Lokesh
authors: L
authors: Bhushan
authors: Ambily
authors: A
authors: Abraham
authors: Nirupam Roy
authors: NR
authors: Choudhury
authors: Vipin Singh
authors: VS
authors: Rana
authors: Sunil Kumar
authors: SK
authors: Mukherjee
authors: Handanahal Subbarao
authors: HS
authors: Savithri
mesh_terms: D020816:Amino Acid Motifs; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004279:DNA, Viral / Q000235:genetics; D020868:Gene Silencing; D020125:Mutation, Missense; D010935:Plant Diseases / Q000235:genetics / Q000821:virology; D010940:Plant Proteins / Q000235:genetics; D014026:Nicotiana / Q000235:genetics / Q000821:virology; D017865:Tospovirus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D010940:Plant Proteins; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins; D004265:DNA Helicases