A large product of cell-free translation of messenger RNA coding for corticotropin.

Polyadenylate-containing RNA prepared from the membrane fraction of bovine anterior pituitary gland was shown to direct the synthesis of a large translation product related to corticotropin (adrenocorticotropic hormone) in a cell-free system derived from wheat germ. This product was identified by immunoprecipitation with specific antibody against corticotropin, followed by electrophoretic analysis of the dissociated immunoprecipitate on sodium dodecyl sulfate-polyacrylamide gel. Further evidence for the identity of the translation product was provided by the presence of a common peptide in the chymotryptic digest of [35S]methionine-labeled cell-free product and in that of authentic corticotropin. The molecular weight of the translation product was estimated to be approximately 35,000, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results indicate that corticotropin messenger RNA directs the cell-free synthesis of a product that contains the amino acid sequence of corticotropin but is much larger than this hormone.