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Fig. 5 | The Journal of Physiological Sciences

Fig. 5

From: Queueing arrival and release mechanism for K+ permeation through a potassium channel

Fig. 5

Graphical representation of the queueing mechanism with comparison to the conventional knock-on mechanism. The concentration-dependent en-queueing rate (black line) and the concentration-independent de-queueing rate (2 → 1; red line) are depicted from Fig. 4b. From the intersection of two lines, the K+ affinity was deduced (red arrow). The 3 → 2 de-queueing rate is also shown as a green line deduced from Fig. 4a. Given the low K+ affinity, the transition from the two-ion-occupied state occurs as either en-queueing or de-queueing in a probabilistic manner. This is the queueing mechanism under the low-affinity regime (right upper cartoon). In contrast, the conventional knock-on mechanism assumes a high-affinity regime. For example, if the Kd value is 0.0004 M (blue arrow), then the de-queueing rate can be deduced (blue broken line). Then, the 2 → 1 de-queueing process never occurs in the physiological concentration range, and the exclusive alternating mode or knock-on mode is allowed (right lower cartoon)

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