THE POLIOVIRUS EMPTY CAPSID SPECIFICALLY RECOGNIZES THE POLIOVIRUS RECEPTOR AND UNDERGOES SOME, BUT NOT ALL, OF THE TRANSITIONS ASSOCIATED WITH CELL ENTRY

Experimental results presented here demonstrate that the poliovirus em pty capsid binds with saturable character to poliovirus-susceptible ce lls, binds preferentially to susceptible cells, and competes with matu re virus for binding sites on cells. Hence, induced changes in the str ucture and/or stability of the particle by RNA encapsidation and virus maturation are not necessary for recognition by receptor. In mature v irus, heat-induced rearrangements mimic those induced by receptor at p hysiological temperatures in several important respects, namely, expul sion of VP4 and externalization of the VP1 N-terminal arm. It is shown here that in the empty capsid the VP1 N-terminal arm is externalized but the VP4 portion of VP0 is not. Thus, these two hallmark rearrangem ents associated with cell entry can be uncoupled.