In vitro studies on the conversion of the biosynthetic precursor of renin

The initial translation product of mouse submaxillary gland mRNA has a molecular weight of about 50,000. We have now translated renin mRNA in frog oocytes which are known to be able to remove the so-called "pre"- or "signal"- sequence from products of injected mRNAs. From these injected oocytes, we could precipitate with antirenin a 48,000 dalton polypeptide. Treatment with kallikrein or trypsin of the oocyte product resulted in a decrease in amount of this 48,000 dalton protein and a corresponding increase in a 45,000 dalton protein, precipitable with antirenin. We conclude that the initial translation product of renin mRNA is a preprorenin of molecular weight 50,000, which in oocytes is enzymatically cleaved to render 48,000 dalton prorenin. Although kallikrein may be a physiological activator of renin, it appears to be not the only one since no mature, 40,000 dalton renin was formed.