Fig. 4

Autoradiograms of two-dimensional phosphopeptide maps of Na⁺,K⁺-ATPase a-subunit after phosphorylation in vitro or in intact cells. (A) Purified Na⁺,K⁺-ATPase phosphorylated with protein kinase C in the presence of 100 µM [γ-³²P]ATP. (B) Purified Na⁺,K⁺-ATPase phosphorylated with cAMP-PK in the presence of 100 µM [µ-³²P]ATP. (C) Na⁺,K⁺-ATPase immunoprecipitated from ³²P-prelabeled choroid plexus incubated with serotonin. (D) Na⁺,K⁺-ATPase immunoprecipitated from ³²P-prelabeled choroid plexus incubated with serotonin plus okadaic acid. (E) Na⁺,K⁺-ATPase immunoprecipitated from ³²P-prelabeled choroid plexus incubated with serotonin plus forskolin. The more prominent phosphopeptides generated by tryptic digestion of Na⁺,K⁺-ATPase phosphorylated with protein kinase C and cAMP-PK are designated (1–4) and (5–6), respectively. Where absent, their position are indicated by dashed circles.