Fig. 8.
Phosphorylation-independent and phosphorylation-dependent modes of modulation of voltage-evoked Kv1.4 currents by Src family protein tyrosine kinase are distinguished by SH3 binding dependence. Peak voltage-gated currents evoked in Kv subunit cRNA-injected X. laevis oocytes by a 1 sec step to +80 mV from a holding potential of –80 mV were measured 9–12 hr after a second injection with H2O, kinase-dead v-Src (v-SrcKD) cRNA, catalytically impaired SrcCI cRNA, or cRNA encoding SrcCI with an inactivated SH3 domain (SrcCISH3ko). The traces that are depicted are averages of the currents measured after the second injection (n > 11 oocytes for each experimental condition). Kv1.4 currents are not modulated significantly by either v-SrcKD or SrcCI, whereas Kv1.4-N-Pro and Kv1.4-C-Pro currents are modulated significantly by both v-SrcKD and SrcCI (Fig. 9). All traces for each channel type are normalized to the peak average current for the water-injected group: Kv1.4-wt = 19.6 μA, Kv1.4-N-Pro = 9.3 μA, and Kv1.4-C-Pro = 13.9 μA.