Phosphorylation of Elongation Factor 1 (EF‐1) by Protein Kinase C Stimulates GDP/GTP‐Exchange Activity

Phosphorylation of the α, β and δ subunits of elongation factor (EF) 1 by protein kinase C results in stimulation of elongation activity up to threefold both in vivo and in vitro [Venema, R. C., Peters, H. I. & Traugh, J. A. (1991) J. Biol. Chem. 266, 11993–11998; Venema, F., C., Peters, H. I. &...

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Veröffentlicht in:European journal of biochemistry 1995-12, Vol.234 (2), p.550-556
Hauptverfasser: Peters, Holme I., Chang, Yu‐Wen Edith, Traugh, Jolinda A.
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Sprache:eng
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Zusammenfassung:Phosphorylation of the α, β and δ subunits of elongation factor (EF) 1 by protein kinase C results in stimulation of elongation activity up to threefold both in vivo and in vitro [Venema, R. C., Peters, H. I. & Traugh, J. A. (1991) J. Biol. Chem. 266, 11993–11998; Venema, F., C., Peters, H. I. & Traugh, J. A. (1991) J. Biol. Chem. 266, 12574–12580]. The α subunit catalyzes the GTP‐dependent binding of amino‐acyl‐tRNA to the ribosome, while the βγ and δ subunits of EF‐1 catalyze exchange of the residual GDP on EF‐1α for GTP. To determine whether the change in elongation rate following phosphorylation by protein kinase C is due to stimulation of GDP/GTP exchange activity, EF‐1 and EF‐1 · valyl‐tRNA‐synthetase have been purified from rabbit reticulocytes, phosphorylated in vitro by protein kinase C and the effect of phosphorylation on nucleotide‐exchange activity analyzed. The α, β and δ subunits are phosphorylated only on serine, and phosphopeptide maps show distinct phosphopeptides for each subunit. Following quantitative phosphorylation of EF‐1 by protein kinase C on the α, β, and δ subunits, a twofold enhancement of the rate of nucleotide exchange over the non‐phosphorylated controls is observed with EF‐1 and EF‐1 · valyl‐tRNA synthetase. Stimulation of nucleotide exchange results in a two‐fold increase in the formation of EF‐1α· GTP · Phe‐tRNA, leading to an increased rate of binding of Phe‐tRNA to ribosomes. The magnitude of stimulation of the exchange rate is similar to that reported previously for the rate of elongation following phosphorylation of EF‐1 by protein kinase C. Thus, the enhancement of EF‐1 activity in response to 4β‐phorbol 12‐myristate 13‐acetate appears to be due to stimulation of the rate of GDP/GTP exchange following phosphorylation of EF‐1 by protein kinase C.
ISSN:0014-2956
1432-1033
DOI:10.1111/j.1432-1033.1995.550_b.x