[The effect of proteolytic cleavage of potato virus X coat protein on its ability to self-assemble with RNA and viral infectivity].

The process of proteolytic cleavage of potato virus X coat protein molecules inside the virions and in the dissociated state in the course of their purification and storage has been studied. In agreement with the previous reports, the intact form (Ps) of the coat protein in the viral particles was found to be gradually cleaved to three discrete lower molecular forms (Pi, Pf, Pu). During the storage of the dissociated coat protein preparations further cleavage was observed with formation of at least three additional lower molecular weight forms (Ppa, Ppb, Ppc). The location of proteolytic cleavage sites leading to formation of Ppa form was determined. The shortened forms Pi, Pf, Pu and Ppa (and possibly Ppc) were found to be incorporated into the viral particles in the course of reconstitution in vitro with the viral RNA. Infectivity of the virus containing only intact (Ps) form of the protein was found to be two to three folds higher than that of the virus containing only Pf form of the coat protein.