PROTEIN-KINASE ACTIVITY ASSOCIATED WITH RNA-POLYMERASE SOLUBILIZED FROM THYLAKOID MEMBRANES

Protein kinase activity was detected in preparations of RNA-polymerase solubilized from chloroplast thylakoid membranes. Investigation of it s substrate specificity indicated that casein suppressed protein kinas e activity, and histone H1 could be used as a phosphorylation substrat e only to a slight extent. The detected protein kinase activity depend ed on the presence of Mg2+ in the reagent medium and was Dot stimulate d by cAMP or polyamines. Action of 6-benzylaminopurine and abscissic a cid in vitro on protein kinase activity associated with solubilized ch loroplast RNA polymerase is shown to be possible. Partial purification of solubilized RNA polymerase by means of centrifugation in a glyceri n centrifugation gradient and chromatography on a column containing ph osphocellulose P-11 did not lead to complete detachment of protein kin ase activity from RNA polymerase activity, which enables us to postula te either the presence of common subunits in these enzymes or a fairly strong bond between them that is not broken by the purification metho ds used.