THE SACCHAROMYCES-CEREVISIAE CDC25 GENE-PRODUCT IS A 180 KDA POLYPEPTIDE AND IS ASSOCIATED WITH A MEMBRANE-FRACTION

In the yeast Saccharomyces cerevisiae, the CDC25 gene product is supposed to interact with ras proteins and adenylate cyclase for progression through the cell division cycle. To identify the CDC25 gene product, we raised antibodies against two hybrid proteins, encoded by in-frame fusions between the E. coli lacZ gene and two different parts of the CDC25 gene. By protein immuno-blotting, we were able to identify the CDC25 gene product as a 180 kDa polypeptide, which we named p180CDC25. It was detected only when the CDC25 gene was overexpressed in a proteases-deficient yeast strain. Subcellular fractionation experiments showed that p180CDC25, as well as ras proteins, is attached to the membrane, even after treatments which release peripheral membrane proteins. © 1990.