CHARACTERIZATION OF AN ATPASE ACTIVITY IN REOVIRUS CORES AND ITS GENETIC ASSOCIATION WITH CORE-SHELL PROTEIN LAMBDA-1

A previously identified nucleoside triphosphatase activity in mammalia n reovirus cores was further characterized by comparing two reovirus s trains,whose cores differ in their efficiencies of ATP hydrolysis. In assays using a panel of reassortant viruses derived from these strains , the difference in ATPase activity at standard conditions was genetic ally associated with viral genome segment L3, encoding protein lambda 1, a major constituent of the core shell that possesses sequence motif s characteristic of other ATPases. The ATPase activity of cores was af fected by several other reaction components, including temperature, pH , nature and concentration of monovalent and divalent cations, and nat ure and concentration of anions. A strain difference in the response o f core ATPase activity to monovalent acetate salts was also mapped to L3/lambda 1 by using reassortant viruses. Experiments with different n ucleoside triphosphates demonstrated that ATP is the preferred ribonuc leotide substrate for cores of both strains. Other experiments suggest ed that the ATPase is latent in reovirus virions and infectious subvir al particles but undergoes activation during production of cores in cl ose association with the protease-mediated degradation of outer-capsid protein mu 1 and its cleavage products, suggesting that mu 1 may play a role in regulating the ATPase.