Thursday, April 20, 2017

Skulachev addendum

This is the final paragraph in the discussion section of the paper by Skulachev, regarding the use of a Na+/K+ concentration gradient across a membrane to store potential energy, convertible to a Na+ or H+ gradient as needed, and why elevated K+ does not have to be a primordial feature of proto-cells:

"One might think that Na+ ions are incompatible with life and this is the reason why K+ is substituted for Na+ in the cell interior. Apparently, it is not the case as, e.g., in halophilic bacteria [Na+]int can reach 2 M [41]. The very fact that some enzyme systems work better in the presence of K+ than of Na+, may be considered as a secondary adaptation of enzymes to the K+-rich and Na+-poor conditions in the cytosol [40]. Besides, it would have been dangerous to couple any work performance with Na+ influx to the cytoplasm if Na+ were a cell poison".

That makes perfect sense to me.



Judith Johnson said...

Peter-I read this and thought you might like to see it if you havent already.

Peter said...

Thanks Judith, a classic on a classic!


Jacquie said...

Peter, I wondered whether you might find these two studies, recently published in The Journal of Clinical Investigation, of interest. (1) High salt intake reprioritizes osmolyte and energy metabolism for body fluid conservation and (2) Increased salt consumption induces body water conservation and decreases fluid intake.

A New York Times article, "Why Everything We Know About Salt May Be Wrong," published on May 8th provides a decent summary. There are links to the papers in the NYT's article. Both are open access.

Peter said...

Thanks Jacquie,

On the to-read list!