Figure 5. The D184N mutation effectively abolishes Ba²⁺ activation of MthK.

Representative current traces at -100 mV showing MthK channel activation at pH 7.3 with 15 mM Ca²⁺ at the cytoplasmic side of a bilayer, followed by replacement with a solution containing 100 mM Ba²⁺ (with no added Ca²⁺), and then back to 15 mM Ca²⁺. The top series of traces shows that 100 mM Ba²⁺ was sufficient to maximally activate wild-type MthK channels (Po = 0.9), whereas no Ba²⁺ activation was observed with D184N mutant channels (0 openings observed, n=5 different bilayer experiments).