Calcium-induced alterations in the functioning of protein serine/threonine and tyrosine kinases in Streptomyces fradiae cells.

In Streptomyces fradiae, calcium ions induce alterations in intensity and specificity of the secondary metabolism and stimulate sporulation. Using in vivo labeling, we demonstrate that in S. fradiae phosphorylation of some proteins are also influenced by Ca2+ added exogenously. Calcium ions at physiological concentration increase phosphorylation of multiple proteins on serine/threonine residues and suppress modification of a 140-kDa protein on tyrosine residues. Assay of protein kinases in situ demonstrated that Ca2+-induced differences in the pattern of protein phosphorylation in vivo are accompanied by Ca2+-dependent cessation of autophosphorylation of 140-kDa tyrosine kinase and by increased autophosphorylation of three serine/threonine kinases with molecular masses of 127, 65, and 31.5 kDa.