Coexpression of human KvLQT1 with human or rat minK subunits increased single-channel conductance from 0.7 pS to 4.5 pS and 6.5 pS, respectively, accounting for the increased macroscopic current.
Does coexpression of minK subunits with KvLQT1 alter the single-channel conductance and current properties in Xenopus oocytes?
The minK subunit increases the macroscopic potassium current of KvLQT1 channels by increasing their apparent single-channel conductance.
Absolute Event Rate: 4.5% vs 0.7%
Expressed in Xenopus oocytes, KvLQT1 channel subunits yield a small, rapidly activating, voltage- dependent potassium conductance. When coexpressed with the minK gene product, a slowly activating and much larger potassium current results. Using fluctuation analysis and single-channel recordings, we have studied the currents formed by human KvLQT1 subunits alone and in conjunction with human or rat minK subunits. With low external K+, the single-channel conductances of these three channel types are estimated to be 0.7, 4.5, and 6.5 pS, respectively, based on noise analysis at 20 kHz bandwidth of currents at +50 mV. Power spectra computed over the range 0.1 Hz-20 kHz show a weak frequency dependence, consistent with current interruptions occurring on a broad range of time scales. The broad spectrum causes the apparent single-channel current value to depend on the bandwidth of the recording, and is mirrored in very "flickery" single-channel events of the channels from coexpressed KvLQT1 and human minK subunits. The increase in macroscopic current due to the presence of the minK subunit is accounted for by the increased apparent single-channel conductance it confers on the expressed channels. The rat minK subunit also confers the property that the outward single-channel current is increased by external potassium ions.
Yang et al. (Tue,) conducted a other in IKs Potassium Channels. Coexpression with minK gene product vs. KvLQT1 subunits alone was evaluated on Single-channel conductance. Coexpression of human KvLQT1 with human or rat minK subunits increased single-channel conductance from 0.7 pS to 4.5 pS and 6.5 pS, respectively, accounting for the increased macroscopic current.