Polyphosphate as a source of phosphoryl group in protein modification in the archaebacterium Sulfolobus acidocaldarius.

The incubation of polyphosphates with the ribosomal fraction of Sulfolobus acidocaldarius leads to the covalent attachment of phosphate to threonine residue(s) of a single 40,000 Mr protein. The hydrolysis kinetics of this protein showed that polyphosphate might be the modifying group. The reaction requires 2 mM Mn2+ ions and is time-dependent. ATP strongly inhibits the transfer of phosphate from polyphosphate, indicating that this process is catalyzed by an enzyme differing from the well-known protein kinases.