Extra Credit (3pts) Consider a voltage-gated sodium channel whose normal threshold membrane potential is -50mV. Suppose mutations have switched the positive and negative amino acids flanking the first transmembrane domain. Please form a prediction and provide your reasoning: Under what conditions will the mutant channel open?
The opening of the channel is caused by changes in ionization state of charged amino acids. If positively and negatively charged amino acids switch, the required ionization level will change in the opposite direction as well. Thus, the channel will open at +50 mV.