Figure 1.

In vitro phosphorylation of the Na channel by CaMKII. Purified GST fusion proteins of the intracellular domains of Na_V1.5 were phosphorylated in vitro with CaMKII in the presence of γ-³²P-labelled ATP. Proteins were separated by SDS–PAGE and transferred to nitrocellulose. Total protein was visualized by Ponceau-S stain (top) and incorporated ³²P was visualized by autoradiography (bottom). Phosphorylation occurred predominantly on the I–II linker, with a smaller amount occurring on the CT domain. NT, amino terminus; CT, carboxyl terminus. I–II, II-III, and III–IV denotes the I–II, II–III, and III–IV interdomain linkers, respectively.