Role of inorganic polyphosphate in promoting ribosomal, protein degradation by the ion protease in E-coli

Inorganic polyphosphate (polyp), a polymer of hundreds of phosphate (P-i) residues, accumulates in Escherichia coli in response to stresses, including amino acid starvation. Here we show that the adenosine 5'-triphosphate-dependent protease Lon formed a complex with polyp and degraded most of the ribosomal proteins, including S2, L9, and L13. Purified S2 also bound to polyp and formed a complex with Lon in the presence of polyP. Thus, polyP may promote ribosomal. protein degradation by the Lon protease, thereby supplying the amino acids needed to respond to starvation.