Inhibition of nuclear-protein phosphorylation in vitro by beryllium.

Endogenous cyclic-nucleotide-independent protein phosphorylation by ATP at pH 6.5 in adult rat liver nuclei in vitro is inhibited by beryllium (Be2+), but under the same conditions nuclear-protein dephosphorylation appears to be insensitive to Be2+. Prior incubation of nuclei with Be2+ is necessary to demonstrate the inhibition of phosphorylation, which increases as the pH is decreased from pH 8.0 to 6.5. The extent of inhibition can be related to the level of nuclear Be2+ binding and, evidence suggests, may be caused by direct or indirect interference by Be2+ with Mg2+ binding sites normally required to facilitate protein phosphorylation.