ISSN:
1432-1424
Keywords:
Chara
;
electrogenic pump
;
chord conductance
;
I–V curve
;
kinetic model
;
computer simulation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The current-voltage curve of theChara membrane was obtained by applying a slow ramp depo- and hyperpolarization by use of voltage clamp. With the progress of poisoning by DCCD (dicyclohexylcarbodiimide) theI–V curve moved by about 50 mV (depolarization) along the voltage axis, reducing its slope, and finally converged to thei d -V curve of the passive diffusion channel. Changes ofi p -V curve of the electrogenic pump channel could be obtained by subtracting the latter from the former. The sigmoidali p -V curve could be simulated satisfactorily by adopting a simple reaction kinetic model. Kinetic parameters of the successive changes of state of the H+ ATPase could be evaluated. Changes of these kinetic parameters during inhibition gave useful information about the molecular mechanism of the electrogenic pump. Depolarization of the membrane potential, decrease of membrane conductance, and decrease of pump current during inhibition of the pump with DCCD are caused mainly by the decrease of conductance of the pump channel. The decrease of this pump conductance is caused principally by a marked decrease of the rate constant for releasing H+ to the outside.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01868773
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