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標題: Avian reovirus core protein mu A expressed in Escherichia coli possesses both NTPase and RTPase activities
作者: Su, Y.P.
Shien, J.H.
Liu, H.J.
Yin, H.S.
Lee, L.H.
關鍵字: nucleoside triphosphate phosphohydrolase;virus ns3 protein;lambda 1;protein;vaccinia virus;genome segments;sigma-a;rna 5-triphosphatase;sequence;binding;nsp2
Project: Journal of General Virology
期刊/報告no:: Journal of General Virology, Volume 88, Page(s) 1797-1805.
Analysis of the amino acid sequence of core protein mu A of avian reovirus has indicated that it may share similar functions to protein mu 2 of mammalian reovirus. Since mu 2 displayed both nucleotide triphosphatase (NTPase) and RNA triphosphatase (RTPase) activities, the purified recombinant mu A (r mu A) was designed and used to test these activities. mu A was thus expressed in bacteria with a 4.5 kDa fusion peptide and six His tags at its N terminus. Results indicated that r mu A possessed NTPase activity that enabled the protein to hydrolyse the beta-gamma phosphoanhydride bond of all four NTPs, since NDPs were the only radiolabelled products observed. The substrate preference was ATP > CTP > GTP > UTP, based on the estimated k(cat) values. Alanine substitutions for lysines 408 and 412 (K408A/K412A) in a putative nucleotide-binding site of r mu A abolished NTPase activity, further suggesting that NTPase activity is attributable to protein r mu A. The activity of r mu A is dependent on the divalent cations Mg2+ or Mn2+, but not Ca2+ or Zn2+. Optimal NTPase activity of r mu A was achieved between pH 5.5 and 6.0. In addition, r mu A enzymic activity increased with temperature up to 40 degrees C and was almost totally inhibited at temperatures higher than 55 degrees C. Tests of phosphate release from RNA substrates with r mu A or K408A/K412A r mu A indicated that r mu A, but not K408A/K412A r mu A, displayed RTPase activity. The results suggested that both NTPase and RTPase activities of r mu A might be carried out at the same active site, and that protein mu A could play important roles during viral RNA synthesis.
ISSN: 0022-1317
DOI: 10.1099/vir.0.82592-0
Appears in Collections:分子生物學研究所

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