Phosphorylation of zymogen granule membrane proteins in intact rat pancreatic acinar cells.

Phosphorylated substrates of molecular weights 130,000, 70,000, and 29,000, were identified by SDS-gel electrophoresis in zymogen granule membranes of rat pancreatic acinar cells incubated in vitro with protein kinase catalytic subunit. However, when intact cells were incubated with [32P]-orthophosphate, only the 29,000 molecular weight protein was phosphorylated.