SCN5A and Brugada syndrome: Replacement of Glu with Gln (E1901Q) or Lys (E1901K) likely disrupted the salt bridge formed by the charge–charge interaction between CaM and Nav1.5 IQ domain and produced a perturbation of CaM regulation of the channel, providing an explanation for the pathological roles of those mutations in Brugada syndrome and LQT3 syndrome.