Native size of protein phosphatase C-I is 38 kDa as determined by immunoprecipitation of the in vitro translation products of total rabbit muscle mRNA

PolyA+ mRNA was prepared from rabbit skeletal muscle. The mRNA was translated in vitro using a rabbit reticulocyte lysate system; the in vitro translation products were labelled using 35-methionine. The products were immunoprecipitated using a monoclonal antibody directed against phosphatase C-I. This enzyme preparation had previously been observed to have a molecular weight of 32 kDa. The immunoprecipitated products were examined by autoradiography after SDS-PAGE. The major immunoprecipitated polypeptides were of 38 kDa and 35 kDa. These findings indicate that the native size of phosphatase C-I is 38 kDa. These results are consistent with the finding in this and other laboratories that if the enzyme preparation is performed in the presence of protease inhibitors, a 38 kDa enzyme, rather than a 32 kDa enzyme is obtained