Genetic and voltage-clamp analysis of a Drosophila potassium channel.

These genetic and voltage-clamp studies have produced evidence that strongly supports the hypothesis that the Shaker locus codes for at least one molecular component of the IA channel. Mutations at the Shaker locus have effects that are specific to IA, and thus a general membrane component is not produced by this locus. Regarding the function of the Shaker product itself, there is evidence that it is at least involved in the inactivation and recovery process of the channel. The evidence so far is also consistent with there being a single Shaker product per channel. Regarding its genetic and developmental properties, IA is apparently completely independent of the other major voltage-activated K+ channel in the membrane, IK. However, only after molecular information becomes available will it become clear whether or not these experiments have revealed clues about the molecular nature of these channels. Ultimately, voltage-clamp experiments, even combined with resourceful genetic tools, can only reveal circumstantial information about the molecular structure of channels. It is hoped, however, that these studies have stimulated interest in the Shaker locus and that the way has been well prepared for molecular studies of the IA channel. The actual molecular characterization of the Shaker locus is already under way (cf. Jan et al., this volume; M. Tanouye , pers. comm .).