Internal application of MTSET to F370C Shaker potassium channels shifts voltage sensor movement, keeping them deactivated at positive potentials, which may be useful for structural studies despite a low modification rate.
May inform structural studies of trapped voltage sensors; leaves open efficiency for routine use in channel research.
For structural studies it would be useful to constrain the voltage sensor of a voltage-gated channel in its deactivated state. Here we consider one Shaker potassium channel mutant and speculate about others that might allow the channel to remain deactivated at zero membrane potential. Ionic and gating currents of F370C Shaker, expressed in Xenopus oocytes, were recorded in patches with internal application of the methanethiosulfonate reagent MTSET. It appears that the voltage dependence of voltage sensor movement is strongly shifted by reaction with internal MTSET, such that the voltage sensors appear to remain deactivated even at positive potentials. A disadvantage of this construct is that the rate of modification of voltage sensors by MTSET is quite low, approximately 0.17 mM(-1).s(-1) at -80 mV, and is expected to be much lower at depolarized potentials.
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Yang et al. (2004) studied this question.
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