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J. Biol. Chem., Vol. 259, Issue 5, 2850-2855, Mar, 1984
GM Hathaway and JA Traugh
The hemoglobin regulator, 2,3-bisphosphoglycerate (glycerate-2,3-P2) has
been shown to modulate the activity of casein kinase II from rabbit
reticulocytes. Kinetic results were obtained with the exogenous substrate,
beta-casein and the endogenous substrates, initiation factors (eIF-) 2 and
3. Experiments carried out to determine the interaction between
glycerate-2,3-P2, Mg2+, substrate, and casein kinase II led to the
following conclusions: 1) glycerate-2,3-P2 inhibition was competitive with
respect to the protein substrate and noncompetitive with respect to ATP; 2)
inhibition was not caused by depletion of ATP-Mg2+ as a consequence of Mg2+
complexation with glycerate-2,3-P2; 3) the response curve for
glycerate-2,3-P2 was cooperative, but the cooperativity decreased as salt
concentration increased; 4) glycerate-2,3-P2 inhibition was dependent on
Mg2+ concentration up to about 5 mM MgCl2 but did not parallel
glycerate-2,3- P2 X Mg2+ complex formation indicating that the Mg2+
dependence was not due to the formation of a glycerate-2,3-P2 X Mg2+
complex; 5) experiments with analogs of glycerate-2,3-P2 showed that the
binary phosphate grouping was important in determining inhibition by
glycerate- 2,3-P2 while the presence of the carboxylate-phosphate pair was
much less important; 6) low levels of glycerate-2,3-P2 stimulated
phosphorylation of beta-casein, eIF-2, and eIF-3; the extent of stimulation
was dependent on the affinity for casein kinase II and the level of the
substrate. These effects were observed in the range of glycerate-2,3-P2
concentrations predicted for intracellular fluctuations in this metabolite.
Therefore, it was concluded that glycerate-2,3-P2 could function both as an
activator and an inhibitor of casein kinase II in the erythroid cell by
binding at the substrate binding site.
Regulation of casein kinase II by 2,3-bisphosphoglycerate in erythroid cells
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