ABSTRACT
The wealth of evidence on K channel structure, function, diversity and differential distribution in animal tissues obtained in the past few years presents us with an amazing panorama that is only now beginning to be revealed. Yet, in spite of the formidable progress that has followed the cloning of a K +-selective channel (Baumann eta/., 1987; Kamb eta/., 1987; Tempel eta/., 1987) our knowledge of the basic principles that govern K channel structure and function is still in its infancy. Such principles concern the most basic phenomena associated with K channel function: their ability to catalyze with high efficiency the passive flow of K + across the cell membrane, their various selectivity and permeation profiles, and the mechanisms of interaction with the membrane electric field (reviewed in Jan and Jan, 1992; Pongs, 1992; Caterall, 1993; Hoshi and Zagotta, 1993; Bezanilla and Stefani, 1994). As a minimum, a basic understanding of K channel structurefunction implies the development of a common set of rules that are sufficient to account for the occurrence of K channels exhibiting variable open conductances, different selectivity sequences and permeation mechanisms. Likewise, the development of the basic rules that give rise to K channel voltage· dependence should suffice to account for the various gating properties of K channels.
