| Comments |
"On the basis of studies of chloride transport mainly at 0°C, the "ping-pong model" for anion exchange was proposed (Gunn and Frohlich, 1979 Frohlich and Gunn, 1986). According to this model, a transport site in the protein, unloaded or loaded with an anion, may either face the internal or the external compartment. Anion transport is achieved by a conformational change in the loaded form of the protein, resulting in translocation of the substrate. Translocation of the unloaded form of the transport site, which represents a potential pathway for conductive anion transport (see Frohlich, 1984), is negligible compared to the translocation of the loaded forms, and is therefore not included in the model. This simple transport model is in accordance with most experimental results obtained in tracer experiments
using monovalent anions at 0°C. However, at high intracellular anion concentrations the model needs
modification because experimental data indicate that anion binding to an internally located allosteric site
prevents anion translocation (Dalmark, 1976 Wieth, 1979 Knnauf and Mann, 1986 Gasbjerg and Brahm, 1991)." See notes beneath tables. Table I is modified ping pong model and table II simple ping pong model |