Concentration of free Ca2+ ions

Value 90 nM Range: ±10 nM
Organism Bacteria Escherichia coli
Reference Gangola P, Rosen BP. Maintenance of intracellular calcium in Escherichia coli. J Biol Chem. 1987 Sep 15 262(26):12570-4. abstract & p.12573 table IIPubMed ID2442165
Method P.12573 note 'a' beneath table II. "Free intracellular calcium was determined from fura-2 fluorescence." P.12571 left column 6th paragraph: "Loading of Fura-2 into E. coli-The pentaacetoxymethyl ester of fura-2, which can permeate the eukaryotic plasma membrane, cannot penetrate the outer membrane of E. coli. However, after treatment with Tris and EDTA, the Gram negative outer membrane is no longer a permeability barrier to hydrophobic compounds (ref 17). In permeabilized cells the ester entered the cytosol and was hydrolyzed. Hydrolysis was monitored by the gradual shift in the excitation spectrum from that of ester, peaking at 370nm, to that of Ca2+ indicator free acid, peaking at 340nm (Fig. 1)."
Comments Abstract: "The concentration of free [Ca2+]i in unstarved cells was maintained at 90 +/- 10 nM, irrespective of the Ca2+ concentration in the extracellular medium." P.12573 left column 2nd paragraph: "The resting Ca2+ in energized E. coli was found to be 90±9 nM, remarkably similar to the levels reported for a variety of eukaryotic cell types (refs 18-22) metabolically active cells [Ca2+]i is maintained at 90nM irrespective of the external extracellular calcium concentration from 10µM to 10 mM."
Entered by Ron Milo, Paul Jorgensen, Mike Springer
ID 100130