Characterization of the binding of S-adenosyl-L-methionine to plasma membranes of HL-60 promyelocytic leukemia cells.
S-Adenosyl-L-methionine (AdoMet) has been found to bind specifically to the plasma membrane of promyelocytic leukemia cells, HL-60. The Kd for AdoMet is 4.2.10(-6) M and the Bmax is 4.0.10(-12) mol/10(7) HL-60 cells. The binding is not related to the adenosine receptor since neither adenosine, ADP, nor ATP affect the ligand-receptor reaction. When HL-60 cells were incubated with physiological concentrations of [methyl-3H]AdoMet (20 microM) at 36 degrees C, AdoMet did not equilibrate with the intracellular pool, nor were any [3H]methyl groups incorporated into nucleic acids or proteins. In contrast, significant amounts of [3H]methyl groups were incorporated into membrane phospholipids. When cells were incubated with 20 microM [methyl-3H]AdoMet, [3H]methyl groups were transferred to phosphatidylethanolamine, -monomethylethanolamine, and -dimethylethanolamine yielding phosphatidylcholine. However, the rate of methyl transfer with AdoMet was only 22% of that observed when cells were incubated with a comparable amount of [methyl-3H]methionine. Both the binding of AdoMet and the methylation of phospholipids were inhibited by exogenous S-adenosyl-L-homocysteine. Therefore, the binding may be linked to a phospholipid methyltransferase.
Duerre
J A
JA
Department of Microbiology and Immunology, University of North Dakota Medical School, Grand Forks 58202.
Gordon
R K
RK
D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute; D008563:Membrane Lipids / Q000302:isolation & purification / Q000378:metabolism; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism; D010743:Phospholipids / Q000302:isolation & purification / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism*; D014316:Tritium; D014407:Tumor Cells, Cultured / Q000378:metabolism*
D008563:Membrane Lipids; D008565:Membrane Proteins; D010743:Phospholipids; D014316:Tritium; D012436:S-Adenosylmethionine