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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.

SummaryIn Streptomyces fradiae, calcium ions induce alterations in intensity and speci city of the secondary metabolism and stimulate sporulation. Using in vivo labeling, we demonstrate that in S. fradiae phosphorylation of some proteins are also in uenced by Ca 2+ added exogenously. Calcium ions at physiological concentration increase phosphorylation of multiple proteins on serine/ threonine residues and suppress modi cation of a 140-kDa protein on tyrosine residues. Assay of protein kinases in situ demonstrated that Ca 2+ -induced differences in the pattern of protein phosphorylation in vivo are accompanied by Ca 2+ -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.

Data on the effects of calcium ions (Ca 2+ ) on processes of morphological and physiological differentiation in cultures of actinomycetes have been reviewed, with emphasis on representatives of the genus Streptomyces . Evidence accumulated thus far regarding the regulatory role of serine-threonine protein kinases in the differentiation and the possible involvement of Ca 2+ -dependent protein kinases in secondary metabolism (including antibiotic biosynthesis) are analyzed. The possibility that regulatory elements of apoptosis (including Ca 2+ -dependent) function in actinomycetes is discussed. A hypothesis is advanced, according to which determinants of antibiotic resistance play a key role in the network of signal transduction systems of actinomycetes.

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