Abstract
When the partially purified P6570 proteolytic factor was added at increasing concentrations to immature core sub-particles of Rauscher leukaemia virus (RLV), we observed an increased cleavage of P6570 (the gag gene product) and P40 (an intermediate cleavage product containing p30) to p30, the major group specific antigen. When examined by electron microscopy the immature cores exhibited a linear decrease in number, with a concomitant increase in the number of mature cores after treatment. Various intermediate structures retaining elements of both immature and mature forms were also observed, suggesting that the in vitro conversion from immature cores to mature cores can occur on a 1:1 basis.