ISSN:
1432-1017
Keywords:
Na, K-pump
;
active transport
;
electrogenic transport
;
current-voltage behaviour
;
Post-Albers scheme
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract The current voltage characteristic of the Na, K pump is described on the basis of a modified Post-Albers cycle. The voltage dependence of the rate constants is derived from the elementary chargetranslocations associated with the single reaction steps. Charge displacements result from movements of the sodium- or potassium-loaded binding sites, as well as from motions of polar groups in the pump molecule. If part of the transmembrane voltage drops between the alkali-ion binding sites and the aqueous solution, the binding constants become voltage-dependent. Depending on the values of the microscopic parameters, the current-voltage characteristic may assume a variety of different shapes. Saturating behaviour results when one or more voltage-independent reaction steps become rate limiting. Non-monotonic current-voltage curves exhibiting regions of negative pump conductance are predicted when, at least in one of the transitions, charge is moved against the direction of overall charge-translocation. The theoretical predictions are compared with recent experimental studies of voltage-dependent pump currents.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00254213
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