The Structure and Biological Function of Polyphosphate-related Proteins

Polyphosphate(polyP),comprising several to hundreds of phosphate(P i) residues linked by phosphoanhydride bonds,the same type of bond that links the phosphates in ATP,has been found in every cell examined,from bacteria to mammals.PolyP-related proteins include polyP-related enzymes and polyPbinding proteins.PolyP-related enzymes,such as polyP kinase(PPK) which catalyzes the reversible synthesis of polyP from the terminal phosphate of ATP,and exopolyphosphatase(PPX) and endopolyphosphatase(PPN) which hydrolyze polyP to shorter chains or P i,have been identified in a variety of micro-organisms.PolyP-dependent kinases that transfer a phosphate from polyP to small molecules such as glucose and nicotinamide adenine dinucleotide(NAD) have also been described.PolyPbinding proteins bind polyP and exert many physiological effects.We speculate on the roles of polyP in biological process are to understand the structures and biological functions of polyP-related proteins.