LOCALIZATION OF REOVIRUS CELL ATTACHMENT PROTEIN ?l ON THE SURFACE OF THE REOVIRION USING IMMUNOFERRITIN ELECTRON MICROSCOPY

Purified reovirus type 3 (strain Dearing) was treated with monoclonal anti-?l antibody conjugated to ferritin and examined in the electron microscope. Virion associated ferritin molecules corresponding to locations of the ?l protein were observed. Electron microsocpy of thin sections of these preparations revealed that ferritin conjugates were localized at the vertices of the viral icosahedron. Reovirus cores possessing spikes and protein ?1, prepared by partial chymotrypsin digestion of intact virions, were similarly treated and examined. Core-associated ferritin molecules were found to be localized at positions corresponding to the tips of the spikes. Such an association was not observed with the cores whose spikes had been removed by alkali treatment. These results provide unequivocal evidence that protein ol is present in icosahedrally-distributed locations, representing tips of reovirus core spikes, on the surface of reovirus particles