A reductionist view of Shaker Kv channel gating. (A) A simplistic gating scheme for a Kv channel with its three activation (A), fast inactivation (I^fast), and slow inactivation (I^slow) gates, corresponding to the S6 bundle crossing, the receptor site of the “chain”-attached ball element in the inner pore cavity, and the selectivity filter element, respectively, each undergoing a conformational transition between closed (C) and open (O) states. In this simplistic gating construct, each thermodynamic square corresponds to a context-dependent cycle that may serve to evaluate how the opening or closing of one gate depends on the conformational state of the other gate. Comparison of the ratio of equilibrium constants for any two parallel transitions would thus provide a quantitative assessment of the degree of coupling between the gates being compared. (B) A simplified cycle that describes the activation and slow inactivation gating of a Shaker Kv channel lacking the fast (N-type) ball and chain inactivation module (see also Fig. 1 in Szanto et al., 2020). The four states are designated C, O, OI, and CI, as commonly done, with the respective general designations given in parenthesis. For simplicity, the gating pathways described in all panels are portrayed by taking the reductionist view, whereby each gating state in a cycle probably represents a composite state.