Fig. 9. One-dimensional phosphopeptide mapping of the 215 kDa ank3 isoform from MDCK cells. An ank3 immunoprecipitate prepared from MDCK cells was incubated in kinase buffer containing [-³²P]-ATP (lane 1), or was heat-treated prior to incubation with purified rat liver CK2 in kinase buffer containing [-³²P]-ATP (lane 2). Following the kinase reactions, the precipitates were analyzed on a 6% SDS polyacrylamide gel, and the gel was stained with GelCode Blue. The 215 kDa ank3 isoform from each in vitro reaction was excised from the gel, electroeluted, and the eluted protein was digested with V8 endoproteinase. The resulting phosphopeptides were analyzed on an 18% SDS polyacrylamide gel. The gel was dried, and ³²P-labeled peptides were detected by autoradiography. Molecular weight markers are indicated to the left of the figure.