FIGURE 3.
Functional properties and degrees of intramolecular FRET for doubly tagged α1S expressed in dyspedic (dysp.) or dysgenic (dysg.) myotubes. All constructs were able to target to the myotube surface, indicated by the presence of discrete fluorescent foci (not shown). In addition to fluorescent puncta, the subunits tagged within the I-II loop (a, d, and e), also displayed a diffuse to reticular intracellular fluorescence when expressed in dyspedic myotubes (indicated by asterisks in the targeting column). Only fluorescent puncta were used for analysis. The column lists the fraction of cells that contracted (contr.) upon electrical stimulation (indicated as the number of responding cells over the number of cells tested) with the number of spontaneously contracting cells (spont.) indicated in parentheses. For each of the constructs, the average current density (pA/pF ± S.D.) is shown together with a representative current trace for a test potential of +30 (b, d, e, and g) or +40 mV (a, c, and f), with calibration bars corresponding to 2 nA and 50 ms. The quotient IY*/IC is a measure of the degree of energy transfer from CyPet to YPet (see text for details).