P~~p~o~la~oa and d~p~osp~o~Ia~~~ of 1%0s0maI protein S8 in starved Ter~&ymena in&c& respectively by Na+ and Ki are amxqmied try changes in int~~l~lar pH which rises by about 0.8 #-I W&S in &Is starving in the presence of Na' ~hospho~la~on of SS) and faIIs by a little more than one pH unit after subsequent addition of K+ (dephosphoryiation of Sl?). In growth-stimulated cells phosphorylation of this protein often shows evident temporal correlations with increases in the rate of protein synthesis and in intracellular pH [4,5]. Phosphorylation of 58 does not occur in growing Tefrahymena [6,7] but can be induced in starved cells (conditions not involving growth factors, hormones, and their receptors and ionic signals) by addition of appropriate cations (Na* but not K+) to the starvation medium [8].Here we show that cations which induce phosphorylation (Na') and dephosphorylation (K+) of S8 in starved Tetrahymena also ihduce a concomitant rise (NaS) or fall (K') in intracellular pH by mechanisms independent of a NaC/H" antiport.
MATERIALS AND METHODS
ReagentsCholine chloride and amitoride were Sigma Grade from Sigma. Radioactive materials for measurement of intracellular pH were Corrarpandence address:
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