摘要
Both avian reovirus core protein σA purified from virus-infected cell extracts and the purified bacterially expressed protein σA (eσA) were characterized for their nucleoside triphosphate (NTP) hydrolysis activity by thin-layer chromotography. Protein σA from both preparations has a nonspecific nucleotidyl phosphatase activity that hydrolyzes four types of NTP to their corresponding nucleoside di- and monophosphates and free phosphate. The divalent cation requirement for this activity of eσA was further examined by the addition of Mn 2+ , Mg 2+ , Ca 2+ , and Zn 2+ ions. NTP hydrolysis by eσA was maximal when Mn 2+ , Mg 2+ , or Ca 2+ concentrations were 5, 4, or 1 mM, respectively. Addition of Mn 2+ or Mg 2+ stimulated the reactions up to 4- or 3-fold, respectively, higher than Ca 2+ (2.2-fold). However, Zn 2+ ion inhibited this activity of eσA. The results suggest that nucleotidyl phosphatase activity of eσA is absolutely dependent on the divalent cations Mn 2+ , Mg 2+ , or Ca 2+ , but not Zn 2+ . Similar results were obtained from the analysis of divalent cation requirements for the protein σA nucleotidyl phosphatase activity. Optimal pH for nucleotidyl phosphatase activity of protein σA from both preparations was determined using reaction mixtures buffered at different pH. The results show that the optimal activities of both proteins were similar and were achieved between pH 7.5 and 8.5. © 2002 Elsevier Science (USA).