Subconductance levels

Chapman, M. L., VanDongen, H. M., and VanDongen, A. M. (1997). Activation-dependent subconductance levels in the drkl K channel suggest a subunit basis for ion permeation and gating. Biophys.J. 72, 708-719. 

A closer look at the single-channel recordings obtained with CFpCF (Fig. 2 and Fig. 3) and with isolated subunit III of CF (Fig. 5), revealed some differences. With subunit III we hardly observed only one type of channel for a longer time period, and we never detected pronounced subconductance levels as shown in Fig. 2 for CF CF.. Obviously, subunit III alone had channel forming ability. Yet it might be that in the presence of the other subunits of CF (as in liposomes with CF CF incorporated), channel formation by subunit III was modified. 

Besides the main conductance state, subconductance levels were found [Fig. 5], showing the same ion selectivity. Generally, channel openings occurred in bursts [Fig. 5] and channel activity declined within 15-30 min after seal formation. Because of this complex gating behaviour, it was not yet possible to study of the kinetic properties of the chloride channel in more detail. 

Fig. 5 Channel activity at +57 mV (symmetrical 20 mM KCl further conditions as in Fig. 2). Only episodes with channel openings are shown (closed times of up to 9 s). A part of the first trace was enlarged (twofold) to emphasize the subconductance levels.

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