Fig. 2.

Responses of wild-type and chimeric Na⁺ channels to coexpressed β₁ subunit. Representative current tracings were recorded in the presence (asterisks) or absence (open circles) of coexpressed hβ₁ during a voltage step to −20 mV from a holding potential of −120 mV. Current amplitudes are scaled and superimposed on the same time axis to illustrate the response of each channel to coexpressed β₁ subunit. The composition of the α subunit chimeras constructed from hSkM1 and hH1 is illustrated next to each tracing. Filled boxes and thick lines represent structures from hH1, and open boxes and thin lines indicate hSkM1 segments. In the hH1 chimeras, vertical arrows point to the transferred hSkM1 sequences. Current decays of all the hSkM1 background chimeras except for hSkM1–P14 were significantly accelerated by coexpressed hβ₁, subunit, and the hβ₁subunit accelerated the inactivation kinetics of chimera hH1–P14.