Characterization of adenohypophysial polypeptides by two-dimensional gel electrophoresis. II. Sulfated and glycosylated polypeptides.

Adenohypophysial sulfated and glycosylated polypeptides were studied by high-resolution two-dimensional polyacrylamide-gel electrophoresis followed by fluorography. The preparations analyzed were the following: (a) homogenates from cow and rat anterior pituitary slices labeled in vitro either with [35S]sulfate or D-[6-3H]glucosamine; (b) materials released from bovine adenohypophysis slices pulse labeled with [35S]sulfate; and (c) purified fractions of bovine prolactin granules stripped by detergent treatment of their limiting membrane. A heterogeneous family of sulfated components, almost all glycosylated, differing in their peptide moieties as well as in their isoelectric points, was revealed in the glandular tissue. The major of these components (apparent Mr approximately 70 000; pI approximately 4.8), which was also highly labeled by L-[3H]-leucine (Zanini, A., and Rosa, P. (1981) Mol. Cell. Endocrinol. 24), might be a secretory protein because it accumulates in the medium during chase incubation of bovine pituitary slices in vitro. This sulfated component, which was more concentrated in the bovine than in the rat gland, was present in purified bovine prolactin granules stripped of their limiting membrane. However, the available evidence suggests that this might not be the only subcellular location of the sulfated polypeptide in the pituitary tissue.