(a) Effect of an increasing number of mut-subunits. The channels are either formed by four monomers (4×wt, 4×mut) or by tetrameric concatamers (wt-wt-wt-wt, mut-wt-wt-wt, mut-mut-wt-wt, mut-mut-mut-wt, mut-mut-mut-mut). All fit parameters are provided by Supplementary Table 1a. (b) Concatamers assemble as tetrameric channels. Expression of either wt-wt-wt-wt or mut-mut-mut-mut channels alone or together with a cRNA ratio 1:1 (N = 14–21). All fit parameters are provided by Supplementary Table 1b. (c) The position of wt-subunits is irrelevant for the concatamer function. The concentration-activation relationships of four concatamers with two wt-subunits and four concatamers with one wt-subunit are plotted. The fit parameters are given in Supplementary Table 1c. The relationships for the concatamers with one wt-subunit were indistinguishable as were the relationships for the concatamers with two wt-subunits (multidimensional t-test with Holm correction, p-value = 1).