Functional subconformations in protein folding: evidence from single-channel experiments.

We study fluctuations in ion conductance and enzymatic rates of the sugar-specific channel-forming membrane protein, Maltoporin, at the single-molecule level. Specifically, we analyze time-persistent deviations in the transport parameters of individual channels from the multichannel averages and discuss our findings in the context of static disorder in protein folding. We show that the disorder responsible for variations in ion conductance does not affect sugar binding, suggesting that Maltoporin can exist in a wide set of fully functional, yet distinctly different, subconformations.