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.
Department of Biophysics, University of Rochester, School of Medicine and Dentistry, New York 14642.
D
D
Restrepo
D J
DJ
Kozody
L J
LJ
Spinelli
P A
PA
Knauf
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