FOOT-AND-MOUTH-DISEASE VIRUS-PARTICLES CONTAIN REPLICASE PROTEIN 3D

An antibody against the Escherichia coli-expressed RNA polymerase of f oot-and-mouth disease virus (FMDV) reacts with the virus in ELISA and radioimmuno-precipitation experiments and with a protein of the disrup ted virus particle in an immunoblot analysis. Treatment of the virus w ith trypsin, which cleaves capsid protein VP1 and a 56-kDa polypeptide present in trace amount in the particles, reduces the level of the re action in ELISA and radioimmunoprecipitation and eliminates the immuno blot reaction. Electron microscopy showed that only approximate to 20% of the virus particles reacted with the anti-polymerase antibody, whe reas most reacted with an antibody against the immunodominant G-H loop of the virus. In the presence of ammonium ions, the expressed polymer ase degrades the RNA of the virus into molecules sedimenting at approx imate to 12 S, indicating that it can act as a hydrolytic as well as a polymerizing enzyme. Moreover, the RNA in trypsin-treated virus parti cles is degraded when incubated at 37 degrees C, suggesting that the c leaved 56-kDa protein still possesses hydrolytic activity. In addition , the anti-polymerase antibody, which inhibits the polymerase activity of the E. coli-expressed protein, also partially inhibits the hydroly tic activity of the previously described endonuclease of the virus par ticle, suggesting that this enzyme is identical with the polymerase or forms part of it.