Protein phosphorylation in the archaebacterium Sulfolobus acidocaldarius.

A number of proteins of the sulphur-dependent archaebacterium Sulfolobus acidocaldarius are phosphorylated in vivo. The extent of phosphorylation depends on the state of growth and is most intense in the late exponential phase. Some of the phosphorylated proteins are strongly associated with the bacterial membrane. Ribosomal proteins and DNA-dependent RNA polymerase are not phosphorylated. Studies in vitro show a high target selectivity. The activity is not increased by cyclic nucleotides. The reaction in vitro is optimal in the presence of Mg2+, Mn2+ or Ca2+. Both serine and threonine residues are modified. Acetate ions do not induce additional phosphorylation.