Specific cleavage of Sendai virus nucleocapsid protein subunits during virus storage

The alteration of whole Sendai virus and especially of its nucleocapsid polypeptides, during storage of the virus at 4 degree C in the allantoic fluids in which it was cultivated, has cultivated, has been studied by sodium dodecyl sulfate gel electrophoresis. During virus storage the nucleocapsid protein subunits with a molecular weight of 60,000 and the putative inner envelope protein with a molecular weight of 38,000 were mainly affected. Both virus components were partially degraded to smaller components. Examination of nucleocapsids isolated from "stored" virus showed that, in addition to the 60,000-molecular weight polypetide component, a smaller polypeptide component with a molecular weight of 46,000 appeared. The relative proportion of the small component increased with the storage period: a kind of specific conversion of large to small components occurred during storage. Since viruses kept in the absence of allantoic fluids revealed no similar modifications of their polypeptides, we concluded that a cellular component present in the allantoic fluids - very likely of enzymatic nature - is responsible for the observed cleavage of virus polypeptides.