31P nuclear magnetic resonance measurements of ATPase kinetics in aerobic Escherichia coli cells

Abstract

We have measured the in vivo unidirectional rates between the terminal phosphate of ATP and intracellular inorganic phosphate (PiIN) in aerobic suspensions of Escherichia coli cells using 31P nuclear magnetic resonance saturation transfer techniques. Typically, the measurements consisted of saturating the ATPgamma resonance and observing a 20 +/- 5% reduction in the intensity of the PiIN resonance. No saturation transfer was observed after incubation with 1 mM dicyclohexylcarbodiimide, an ATPase inhibitor. From the measured decrease in intensity of PiIN coming from saturation transfer, the apparent unimolecular rate constant of PiIN to ATP was calculated to be 0.6 +/- 0.15 sec-1.