title: The RNA triphosphatase domain of L protein of Rinderpest virus exhibits pyrophosphatase and tripolyphosphatase activities.
abstract: L protein of the Rinderpest virus, an archetypal paramyxovirus possesses RNA-dependent RNA polymerase activity which transcribes the genome into mRNAs as well as replicates the RNA genome. The protein also possesses RNA triphosphatase (RTPase), guanylyltransferase (GTase) and methyltransferase enzyme activities responsible for capping the mRNAs in a conventional pathway similar to that of the host pathway. Subsequent to the earlier characterization of the GTase activity of L protein and identification of the RTPase domain of the L protein, we report here, additional enzymatic activities associated with the RTPase domain. We have characterized the pyrophosphatase and tripolyphosphatase activities of the L-RTPase domain which are metal-dependent and proceed much faster than the RTPase activity. Interestingly, the mutant proteins E1645A and E1647A abrogated the pyrophosphatase and tripolyphosphatase significantly, indicating a strong overlap of the active sites of these activities with that of RTPase. We discuss the likely role of GTase-associated L protein pyrophosphatase in the polymerase function. We also discuss a possible biological role for the tripolyphosphatase activity hitherto considered insignificant for the viruses possessing such activity.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, India.
authors.forename: Piyush Kumar
authors.initials: PK
authors.lastname: Singh
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012, India. shaila@mcbl.iisc.ernet.in.
authors.forename: Shaila Melkote
authors.initials: SM
authors.lastname: Subbarao
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000378:metabolism; D011755:Pyrophosphatases / Q000378:metabolism*; D012315:RNA Caps / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism; D012302:Rinderpest virus / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D012315:RNA Caps; D012333:RNA, Messenger; D014764:Viral Proteins; D009713:Nucleotidyltransferases; C020842:guanylyltransferase; D012324:RNA-Dependent RNA Polymerase; D017766:Acid Anhydride Hydrolases; D011755:Pyrophosphatases; C023090:RNA triphosphatase; C023193:tripolyphosphatase
keywords: Pyrophosphatase; RNA Triphosphatase domain; Rinderpest virus L protein; Tripolyphosphatase; mRNA Capping