Fig. 4.

The β_1aAAA mutation has only a minor effect on intracellular Ca²⁺ transients. (A) Representative intracellular Fluo-4 Ca²⁺ recordings from relaxed myotubes expressing zebrafish and rabbit WT β_1a (upper panel) or β_1aAAA mutant subunits (lower panel). Pronounced intracellular Ca²⁺ transients in response to 200-ms test pulses with similar kinetics were recorded with all constructs. Differences in transient size with β_1aAAA can be explained by slight differences in expression levels as indicated by differences in intramembrane charge movement recordings (insets). (B) Voltage dependence curves of ΔF/F₀ were corrected for differences in expression levels by normalizing ΔF/F₀ to Q_max. Transients were slightly shifted towards more positive potentials for the β_1aAAA constructs.