The MlotiK1 channel transports ions along the canonical conduction pore

Although the cyclic nucleotide‐modulated potassium channel from Mesorhizobium loti , MlotiK1, is easily studied using a 86 Rb + flux assay, its comparatively low activity raises serious concerns about the integrity of the purified protein. We investigated the pathway of uptake using a multi‐pronged approach. First, we probed the conduction pathway using quaternary ammonium compounds known to block conduction in eukaryotic K + channels. Second, we examined the effect of chemical modification of putative pore‐lining residues. Our results are consistent with ions traversing MlotiK1 along a conduction pathway like that of the eukaryotic channels, but at a much slower rate.