Cl-Cl exchange in promyelocytic HL-60 cells follows simultaneous rather than ping-pong kinetics.
The intra- and extracellular chloride concentration dependencies of the rate of Cl-Cl exchange in human promyelocytic leukemic HL-60 cells were studied by means of radioactive isotope (36Cl) efflux measurements. Efflux of isotope from cells follows an exponential time course. The Cl-Cl exchange flux follows Michaelis-Menten kinetics as a function of both intra- and extracellular chloride concentrations. The ratio of the maximum exchange velocity to the apparent Michaelis constant for both extracellular and intracellular substrate increases as a function of trans Cl concentration, indicating that Cl-Cl exchange in the HL-60 cell does not follow ping-pong kinetics. A kinetic scheme in which extracellular and intracellular chloride ions bind in random order to the transporter and are then translocated simultaneously can adequately model the experimental data.
Restrepo
D
D
Department of Biophysics, University of Rochester, School of Medicine and Dentistry, New York 14642.
Kozody
D J
DJ
Spinelli
L J
LJ
Knauf
P A
PA
D000837:Anion Exchange Resins / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
D000837:Anion Exchange Resins; D002712:Chlorides