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Quantification of ATP consumption in ion transport system

Wayne Albers rwalbers at helix.nih.gov
Sat Dec 30 15:47:38 EST 1995

In article <4bs4ap$17ag at saba.info.ucla.edu>, sherlock at ucla.edu (Andrew) wrote:

> Does anyone know of an efficient method to quantify ATP consumption by
> an ion transport system accross a bilypid layer membrane?

Depends on the rest of your experimental set-up------  reconstitution of a
purified transport system into liposomes or "inside-out" membrane vesicles
is the most practical.  Many such experiment have been done, e.g. for
stoichiometry of cation transport, using labelled ATP and determining the
ratio of cation uptake to Pi production.  Such measurements are not
feasible in single bilayer systems (Rudin-Mueller type) because of the
small amount of transported ion relative the the amount of ATP in the
system.  Classical measurements of Na+ and K+ transport were done in red
cells and of Ca2+ in SR vesicles, but measurements in many other cell
preparations are confounded by high extraneous ATP utilization.

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